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Ind 2 Bibliographic Data 

01970cama22004097a-4500 

19038418 

20160331174057.0 

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906 

925 0 

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050 0 
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ta acquire tb 1 shelf copies t* policy default 
ta 2009655237 
ta DLC *c DLC 
Ja n-us— 

0 taU393tb ,S7Div.19, v. 1 
0 |a Miscellaneous weapons 

ta Washington, D.C. : tb Office of Scientific Research and 
Development, National Defense Research Committee, Division 6, tc 
1946. 

ta : tb illustrations, charts, plans ; tc 27 cm 
ta text tb txt t2 rdacontent 
ta unmediated tb n t2 rdamedia 
ta volume tb nc t2 rdacarrier 

ta Summary technical report of Division 19, NDRC ; tv v. 1 
ta "Manuscript and illustrations for this volume were prepared for 
publication by the Summary Reports Group of the Columbia University 
Division of War Research under contract OEMsr-1 131." 
ta Half-title: Summary technical report of the National Defense 
Research Committee. 

ta Includes bibliographical references (pages 139-146. (v. 1)) and 
index. 

ta The subject indexes of all Summary Technical Report volumes are 
combined in a master index printed in a separate volume, 
ta LC Science, Business & Technology copy no. 80. t5 DLC 
ta In a set of declassified documents held as a collection by the 
Library of Congress. t5 DLC 
0 ta Military research fz United States. 

0 ta Weapons. 

0 ta Armor. 

0 ta Fuzes (Ordnance) 

0 ta Communications, Military. 


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SUMMARY TECHNICAL REPORT 


OF THE 

NATIONAL DEFENSE RESEARCH COMMITTEE 


O 

CO 

CO ^ 
CO 


This document contains information affecting the national defense of the 
United States within the meaning of the Espionage Act, 50 U. S. C., 31 and 32, 
as amended. Its transmission or the revelation of its contents in any manner 
to an unauthorized person is prohibited by law. 



This volume is classified RESTRICTED in accordance with security regula- 
tions of the War and Navy Departments because certain chapters contain 
material which was RESTRICTED at the date of printing. Other ^lajiters 
may have had a lower classification or none. The reader is advised to coifeult 
the War and Navy agencies listed on the reverse of this page for the current 
classification of any material. 


regraded unclassified 

ER SEC MM Y BY TAG URjfl 2 U ±- 


CHIEF OF ENGINEERS 


Manuscript and illustrations for this volume were prepared for 
publication by the Summary Reports Group of the Columbia 
University Division of War Research under contract OEMsr-1131 
with the Office of Scientific Research and Development. This vol- 
ume was printed and bound by the Columbia University Press. 

Distribution of the Summary Technical Report of NDRC has been 
made by the War and Navy Departments. Inquiries concerning the 
availability and distribution of the Summary Technical Report 
volumes and microfilmed and other reference material should be 
addressed to the War Department Library, Room 1A-522, The 
Pentagon, Washington 25, D. C., or to the Office of Naval Re- 
search, Navy Department, Attention: Reports and Documents 
Section, Washington 25, D. C. 


Copy No. 



REGRADED UNCLASSjFii 
BER SEC ARM Y BY U € 

-£ ONLY 


is KL 




SUMMARY TECHNICAL REPORT OF DIVISION 19, NDRC 

VOLUME 1 


MISCELLANEOUS 

WEAPONS 


OFFICE OF SCIENTIFIC RESEARCH AND DEVELOPMENT 
VANNEVAR BUSH, DIRECTOR 

NATIONAL DEFENSE RESEARCH COMMITTEE 
JAMES B. CONANT, CHAIRMAN 

DIVISION 19 
H. M. CHADWELL, CHIEF 



NATIONAL DEFENSE RESEARCH COMMITTEE 



James B. Conant, Chairman 
Richard C. Tolman, Vice Chairman 
Roger Adams Army Representative 1 

Frank B. Jewett Navy Representative 2 

Karl T. Compton Commissioner of Patents 3 

Irvin Stewart, Executive Secretary 


1 Army representatives in order of service: 


2 Navy representatives in order of service: 


Maj. Gen. G. V. Strong 
Maj. Gen. R. C. Moore 
Maj. Gen. C. C. Williams 
Brig. Gen. W. A. Wood, Jr. 


Col. L. A. Denson 
Col. P. R. Faymonville 
Brig. Gen. E. A. Regnier 
Col. M. M. Irvine 


Col. E. A. Routheau 


Rear Adm. H. G. Bowen Rear Adm. J. A. Furer 

Capt. Lybrand P. Smith Rear Adm. A. H. Van Keuren 

Commodore H. A. Schade 
3 Commissioners of Patents in order of service: 

Conway P. Coe Casper W. Ooms 


NOTES ON THE ORGANIZATION OF NDRC 



imittei 


The duties of the National Defense Research Committee 
were (1) to recommend to the Director of OSRD suitable 
projects and research programs on the instrumentalities of 
warfare, together with contract facilities for carrying out 
these projects and programs, and (2) to administer the tech- 
nical and scientific work of the contracts. More specifically, 
NDRC functioned by initiating research projects on re- 
quests from the Army or the Navy, or on requests from an 
allied government transmitted through the Liaison Office 
of OSRD, or on its own considered initiative as a result of 
the experience of its members. Proposals prepared by the 
Division, Panel, or Committee for research contracts for 
performance of the work involved in such projects were 
first reviewed by NDRC, and if approved, recommended to 
the Director of OSRD. Upon approval of a proposal by the 
Director, a contract permitting maximum flexibility of 
scientific effort was arranged. The business aspects of the 
contract, including such matters as materials, clearances, 
vouchers, patents, priorities, legal matters, and administra- 
tion of patent matters were handled by the Executive Sec- 
retary of OSRD. 

Originally NDRC administered its work through five 
divisions, each headed by one of the NDRC members. 
These were : 

Division A — Armor and Ordnance 

Division B — Bombs, Fuels, Gases, & Chemical Problems 
Division C — Communication and Transportation 
Division D — Detection, Controls, and Instruments 
Division E — Patents and Inventions 


In a reorganization in the fall of 1942, twenty-three ad- 
ministrative divisions, panels, or committees were created, 
each with a chief selected on the basis of his outstanding 
work in the particular field. The NDRC members then be- 
came a reviewing and advisory group to the Director of 
OSRD. The final organization was as follows: 


Division 1 — Ballistic Research 
Division 2 — Effects of Impact and Explosion 
Division 3 — Rocket Ordnance 
Division 4 — Ordnance Accessories 
Division 5 — New Missiles 
Division 6 — Sub-Surface Warfare 
Division 7 — Fire Control 
Division 8 — Explosives 
Division 9 — Chemistry 
Division 10 — Absorbents and Aerosols 
Division 11 — Chemical Engineering 
Division 12 — Transportation 
Division 13 — Electrical Communication 
Division 14 — Radar 
Division 15 — Radio Coordination 
Division 16 — Optics and Camouflage 
Division 17 — Physics 
Division 18 — War Metallurgy 
Division 19 — Miscellaneous 
Applied Mathematics Panel 
Applied Psychology Panel 
Committee on Propaga 
Tropical Deterioration! Administrative 


NDRC FOREWORD 


A s events of the years preceding 1940 revealed 
more and more clearly the seriousness of the 
world situation, many scientists in this country came 
to realize the need of organizing scientific research for 
service in a national emergency. Recommendations 
which they made to the White House were given care- 
ful and sympathetic attention, and as a result the 
National Defense Research Committee [NDRC] was 
formed by Executive Order of the President in the 
summer of 1940. The members of NDRC, appointed 
by the President, were instructed to supplement the 
work of the Army and the Navy in the development 
of the instrumentalities of war. A year later, upon the 
establishment of the Office of Scientific Research and 
Development [OSRD], NDRC became one of its 
units. 

The Summary Technical Report of NDRC is a 
conscientious effort on the part of NDRC to sum- 
marize and evaluate its work and to present it in a 
useful and permanent form. It comprises some 
seventy volumes broken into groups corresponding 
to the NDRC Divisions, Panels, and Committees. 

The Summary Technical Report of each Division, 
Panel, or Committee is an integral survey of the work 
of that group. The first volume of each group’s re- 
port contains a summary of the report, stating the 
problems presented and the philosophy of attacking 
them, and summarizing the results of the research, 
development, and training activities undertaken. 
Some volumes may be “state of the art” treatises 
covering subjects to which various research groups 
have contributed information. Others may contain 
descriptions of devices developed in the laboratories. 
A master index of all these divisional, panel, and com- 
mittee reports which together constitute the Sum- 
mary Technical Report of NDRC is contained in a 
separate volume, which also includes the index of a 
microfilm record of pertinent technical laboratory 
reports and reference material. 

Some of the NDRC-sponsored researches which 
had been declassified by the end of 1945 were of suffi- 
cient popular interest that it was found desirable to 
report them in the form of monographs, such as the 
series on radar by Division 14 and the monograph on 
sampling inspection by the Applied Mathematics 
Panel. Since the material treated in them is not dupli- 


cated in the Summary Technical Report of NDRC, 
the monographs are an important part of the story of 
these aspects of NDRC research. 

In contrast to the information on radar, which is of 
widespread interest and much of which is released to 
the public, the research on subsurface warfare is 
largely classified and is of general interest to a more 
restricted group. As a consequence, the report of 
Division 6 is found almost entirely in its Summary 
Technical Report, which runs to over twenty vol- 
umes. The extent of the work of a Division cannot 
therefore be judged solely by the number of volumes 
devoted to it in the Summary Technical Report of 
NDRC: account must be taken of the monographs 
and available reports published elsewhere. 

Hampered and confused by the unfamiliar restric- 
tions of military security, many civilian scientists 
engaged in NDRC research found themselves par- 
ticularly hindered by the lack of opportunity for free 
and open consultation. This was particularly true for 
Division 19 under the leadership of Harris M. Chad- 
well. Few even in the military services knew of its 
existence, and still fewer knew of its operations. 
Working closely with the Office of Strategic Services, 
it was devoted to the development of instruments for 
sabotage and espionage in enemy-held territory — a 
subject not widely discussed even in time of peace. 

Since few men were cognizant of the Division’s ac- 
tivities, this Summary Technical Report, prepared 
under the direction of the Division Chief and author- 
ized by him for publication, will have only a very lim- 
ited distribution. It is regrettable that this is neces- 
sary and that wider recognition cannot be given to 
the men of the Division and its contractors. Their 
contributions made possible to a large extent the suc- 
cessful operations of their country and its allies in the 
war of the underground. Their efforts were those of 
men of high integrity, imagination, and competence, 
cooperating loyally and brilliantly in the defense of 
their country. 

Vannevar Bush, Director 
Office of Scientific Research and Develo 


J. B. Con ant, Chairman 
National Defense Resear n 




4ft 


REGRADED UNCLASSIFIED 

ORDER SEC ARMY BY TAG ^ ER ]T 


ft 







FOREWORD 


I N its volume of the Summary Technical Report, 
Division 19 is a special case among the divisions 
of NDRC. Throughout its existence this division did 
not conform to the established practice of distribut- 
ing reports; it received very few problems from the 
Army and Navy through the usual channels and 
limited its activity almost exclusive^ to problems 
submitted by an intimate and informal liaison with 
the Office of Strategic Services and the British liaison 
officers assigned to that group. Since the true nature 
of the work done by OSS has been well publicized, 
it can be logically inferred that the developments 
produced by Division 19 under the ambiguous 
title Miscellaneous Weapons were connected with the 
underground organizations established in Europe 
prior to D-day, with special attention given to sabo- 
tage and unorthodox warfare. The unusual handling 
of the division’s reports is thereby explained. 

During the course of its existence, however, the 
division, by accident rather than design, did work on 
several problems of value and interest to the older 
and more orthodox branches of the Armed Services. 
In such instances, there was complete exchange of in- 
formation on a very informal basis with the Service 
groups concerned, and guidance and valuable in- 
formation were thereby provided for the division’s 
contractors. It is hoped that the division has assisted 
the research programs of the Army and Navy. 

The largest contract under the division was with 
Ford, Bacon, and Davis, Inc., for the operation of a 
central laboratory known as the Maryland Research 
Laboratories [MRL] located near Washington. 
Members of the staff of that laboratory contributed, 
in one way or another, to the development of most of 
the devices described in this volume and they coop- 
erated wholeheartedly with other contractors of the 
division. 

Throughout the complete program of Division 19, 
Dr. Warren C. Lothrop served as Technical Aide. 
The major part of this volume of the Summary Tech- 


ters 18, 19 and 20 were written by Mr. S. Reid 
Warren, Jr., of the Moore School of Electrical En- 
gineering of the University of Pennsylvania, where 
the devices described in these chapters were devel- 
oped. To the authors I wish to express my gratitude. 

It was originally decided that there should be no 
Summary Technical Report for Division 19, but, in 
view of the past exchange of information and the fact 
that many of the devices were known to the older 
Services as a result of the above relationship, it was 
finally decided that those parts of the division’s work 
which could properly be called legitimate should be 
recorded and should constitute its Summary Techni- 
cal Report. From this point of view, the four parts of 
this volume have been prepared. 

Unfortunately, in comparison with the other vol- 
umes of the STR, the usefulness of the material is 
limited, since microfilming of the references con- 
tained in the various bibliographies has been omitted. 
This decision was made by high authority in order to 
keep to a minimum all extraneous information in the 
division’s reports and to keep small the circle of people 
who are thoroughly acquainted with the unortho- 
dox aspects of the activity. However, if any pq,rt of 
this volume should be of special interest to some 
Service group, it is believed that there will be little 
difficulty in arranging for access to specific portions 
of the division’s files or the files of the Strategic Serv- 
ice Unit, War Department, by the appropriate per- 
sonnel. Many of the reports to which reference is 
made are already in the hands of those groups of the 
Army and Navy who are primarily concerned. 

Despite these limitations, it is hoped that this vol- 
ume will be of value, as much for the description of 
unsuccessful work as for the description of devices 
which, in production and field use, proved successful 
in many special operations. 


H. M. Chad well 




















































































































































































































' 










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uoY .9atuio7 srij lo iimaiqmi oJ in ^ bus enoqoi 



This volume, like the seventy others of the Sum- 
mary Technical Report of NDRC, has been writ- 
ten, edited, and printed under great pressure. 
Inevitably there are errors which have slipped past 
Division readers and proofreaders. There may be 
errors of fact not known at time of printing. The 
author has not been able to follow through his 
writing to the final page proof. 

Please report errors to: 

JOINT RESEARCH AND DEVELOPMENT BOARD 
PROGRAMS DIVISION (STR ERRATA) 

WASHINGTON 25, D. C. 

A master errata sheet will be compiled from these 
reports and sent to recipients of the volume. Your 
help will make this book more useful to other 
readers and will be of great value in preparing any 


revisions. 


CONTENTS 


CHAPTER PART I PAGE 

WEAPONS 1 

1 Rocket Launchers 3 

2 Oil Slick Igniter (NO-234) 8 

3 Grenade, Hand, Fragmentation, T-13 (Beano) .... 15 

4 WP Beano (OD-176) 23 

5 Spigot Mortar 28 

6 Slow Burning Explosives (SBX) 33 

7 Special Remote-Firing Devices (NR-109) 40 

PART II 

SPECIAL FUZES 43 

8 Sympathetic Fuze or Concussion Detonator 45 

9 Pencil (SRA-3) Firing Device, Delay Type, M-l ... 54 

10 Mark II Pencil 66 

11 Incendiary Pencil (SRI) 71 

12 Clockwork Time Delay (Demolition Firing Device Mark 3) 74 

13 Bases for Time Delay Fuzes 80 

14 Radio-Controlled Switch 87 


PART III 

COMMUNICATION DEVICES 


93 


15 A Short-Range Induction Field Communicating System 

(IFT-IFL) 95 

16 Short-Range Communication by Means of Low Frequency 

Currents in Water 

17 A Compact Microwave Transmitter and Receiver and 

Miscellaneous Communicating Devices 


regraded umclass^ed 
ORDER SEC ARMY BY TAG ^ 



CONTENTS 




CHAPTER PART IV PAGE 

FIELD ACCESSORIES 113 

18 Parachute Locating Devices 115 

19 Military Adhesives 119 

20 Aids to Intelligence 122 

21 Dog Deception 127 

22 Water Purifier 129 

23 Quieting Outboard Motors 133 

Glossary 137 

Bibliography 139 

OSRD Appointees 147 

Contract Numbers 148 

Project Numbers 149 

Index 151 



PART I 


WEAPONS 


During World War II, as never before, science was 
enlisted for the development of new weapons of war- 
fare utilizing many kinds of scientific principles. The 
results were remarkable, and warfare thereby as- 
sumed previously unthought of tactical aspects. Con- 
current with this was the acceptance by the Army 
and Navy of ideas of a novel and unorthodox type. 
The most spectacular and larger contributions of 
OSRD to the military are found elsewhere in the 
Summary Technical Report. Very frequently these 
were of a large scope. 

The work of Division 19 described in this part on 
weapons, while retaining the novel and unorthodox 
features to an enhanced degree, resulted in no dis- 
covery which could rank with radar, the atomic 
bomb, or the proximity fuze in its great effect on mil- 
itary operations. Nevertheless, a number of small and 
useful devices were developed primarily of value to 
the individual soldier or small groups, in operations 
exemplified by commando raids and scouting parties. 
In this more limited and very specialized field, the 
weapons described in Part I are believed to have real 
value and to bring close to the individual results of 
modern technological development. A neglected field 
was thereby opened and partly explored. 

Considerable imaginativeness has been shown in 
these developments, and this demands an equal 
imaginativeness on the part of potential users. The 
very unorthodox nature of some of the devices will of 
necessity mean that the field of hand application is a 
narrow one at best, but this is not to say that in that 


narrow field their value may not be of the highest de- 
gree to a given individual in a given situation. In such 
cases it may far outweigh the rather limited demand 
which might be foreseen and because of which Army 
and Navy procurement might, with logic, hesitate. 

To those who have been close to the development 
of these weapons, it has always seemed that they 
might well supplement for surprise use the more or- 
thodox devices now issued to special troops. Only one 
of the developments described in Part I may have a 
broader scope; this is the impact spherical hand gre- 
nade known as Beano and described in Chapter 3. For 
the most part the weapons are explosive in nature, 
there being only one which has a truly incendiary 
action among them; this is the oil slick- igniter de- 
scribed in Chapter 2. Others such as Beano loaded 
with white phosphorus (see Chapter 4) and slow 
burning explosives (see Chapter 6) lie intermediate 
between explosive and incendiary devices. However, 
without exception all the weapons in their present 
state are of a size suitable for use by a single person 
and should probably be presented as items for indi- 
vidual issue to special scouting or raiding par- 
ties. 

The groups in the Army and Navy who have been 
acquainted with these devices and who would appear 
to find them of value would include particularly the 
Army Ground Forces, the Corps of Engineers, the 
Chemical Warfare Service, the Ordnance Depart- 
ment, the Bureau of Ordnance, and the Marine 
Corps. 


REGRADED UNCLASSSHED 
088ES SEC ARMY BY TAG PER jjyj 0 43 


FOR OFFICIAL USE ONLY 



l 

















































Chapter 1 

ROCKET LAUNCHERS 


1.1 INTRODUCTION 

The striking power of an individual foot soldier 
has been greatly enhanced by the development of 
portable rocket weapons of which the M6A3 or 
Bazooka of the Americans and the PIAT gun of the 
British are the foremost. Each of these, of course, is 
provided with its launcher and, as generally used, is 
a shoulder weapon. That there may be occasionally 
a need for firing as a booby-trap or delayed action de- 
vice is also well recognized and has been indicated in 
publications of the Ordnance Department and the 
Corps of Engineers. In this case, it is customary to 
use, as the launcher, the original packing tube in 
which the rocket round is delivered to the field. A 
small amount of work on this application was done 
by the division and is discussed below. 

The Bazooka is, however, not a very formidable 
rocket when compared to those used by and against 
ships and aircraft. It would seem logical therefore to 
make one of these heavier and more destructive 
rounds available to the individual soldier for his use 
against some specially selected and unapproachable 
target. This idea resulted in the perfection of a port- 
able, re-usable, but expendable launcher small and 
light enough to be carried by an individual, and simple 
enough to be erected and fired easily, either man- 
ually or by trip wire or time delay fuze (see Chap- 
ter 9). This work using the 3.55-in. spin stabilized 
rocket (SSR) developed at California Institute of 
Technology [CIT] under Division 3 of NDRC is the 
subject of Section 1.3. 

1.2 LAUNCHING M6A3 BAZOOKA 

ROCKETS FROM THEIR CONTAINERS 

For the use contemplated, three separate minor 
developments were required: a simple unadjustable 
sight representing a separate item of equipment, a 
trip wire firing system, and a time delay firing system. 

1.2.1 The Sight 

This consisted of thin sheet steel 8 in. long, in. 
wide, and 2J£ in. high, dimensions which fitted the 
standard tubular cardboard containers in which the 
2.36-in. Bazooka rounds were issued to the field. 
Mounted laterally on this base was a bead and pin- 
hole sighting system analogous to the standard 7'ifle 


sight, but ending in a mirror, of either glass or pol- 
ished metal, mounted obliquely to allow convenient 
observation of the target during final location of the 
cardboard carton in the ground. The sight as finally 
produced by the Office of Strategic Services was 
rigidly constructed to provide an accurate range of 
100 ft, a distance selected as optimum from the 
standpoint of rocket performance and operational 
needs. It would be possible to alter this range slightly 
but not significantly. 

The performance for this sight is illustrated by 
Table 1, which was obtained from firing five live 
rounds of M6A3 ammunition from their packing con- 
tainers after aiming with the reflecting sight. 2 The 

Table 1. Performance of M6A3 sight. 


Shot No. 

Vertical deviation 
inches 

Lateral deviation 
inches 

1 

42 low 

20 right 

2 

8 low 

0 

3 

15 high 

8 left 

4 

0 

0 

5 

25 low 

0 


target was at a distance of 95 to 97 ft, the wind veloc- 
ity was 2 mph or less, and the temperature was 78 F. 
Averaging of the data indicated a center of impact 
falling 12 in. below and 3 in. to the right of the aim- 
ing point, an aberration which was not considered 
serious. 

1.2.2 Trip Wire Firing 1 

The standard Bazooka launcher is equipped with 
dry cells which provide electric firing of the round. 
For booby-trap use, batteries were unreliable because 
in the indeterminate period of inactivity following 
the setting up of the trap they might go dead. In 
their place was substituted a simple, mechanically 
operable electric magneto which was found by test to 
deliver a current sufficient to insure firing the round 
and which, of course, had an indefinite shelf life. The 
recommended, standard Navy Mark 22 Magna vox 
magneto was connected to the wires from the electric 
squib located in the tail of the rocket motor and then 
attached to a trip wire suitably mounted across a road 
or trail. A sharp pull on the trip wire was sufficient to 
turn over the magneto and deliver to Bjje electric 
squib a surge of current adequatedor fimig it. 


regraded unclassified 
ORDER SEC ARMY BY TAG HU 



4 


ROCKET LAUNCHERS 


1.2.3 Time Delay Firing 1 

In cases where it was desirable to aim and plant 
the round, and then to fire it at some future pre- 
selected time, a different but equally simple system 
was supplied. The electric squib was removed from 
the motor and a short length of safety fuze, bearing 
several slanting cuts, was introduced into the pro- 
pellant charge. The other end of the fuze was con- 
nected in the standard manner to a time delay Pencil 
having a spring snout (see Chapter 9 and Section 
11.3.3). 

1.2.4 Operation 1 

The rocket round in its original packing carton 
could be set up in some concealed place and trained 
on a spot in a road, for example, or on a nearby target 
which could not be closely approached. The proce- 
dure was to embed the tubular carton, the closed 
ends of which had been cut off to make it an open 
tube, in the earth, training it on the target with the 
aid of the sight which was laid on top of the tube. In 
order to avoid disturbing the tube after final sight- 
ing, it was found best to have the rocket with safety 
pin removed in the tube before final aim was taken 
and the sight removed. It was important that the 
tube be solidly embedded in soil, which should prefer- 
ably not be sandy. When 14 rounds were fired under 
these conditions at a target 95 ft distant and with the 
sight fixed at 1 degree elevation, all fell within a 5-ft 
radius circle and 50 per cent in an 18-in. circle, the 
center being the point of aim (see Figure 1). 



Figure 1 . Dispersion — M6A3 rockets. 


1.3 ROCKET LAUNCHER FOR 

3.55-INCH SSR 3,8 

Upon the advice and through the cooperation and 
support of Division 3 and their contractor CIT a se- 
lection of a rocket more powerful and effective than 
the 2.36-in. Bazooka was made. The choice fell on 
the 3.55-in. spin stabilized rocket (SSR) which Divi- 
sion 3 had developed to satisfy a special Navy re- 
quirement. 5, 6 In the following discussion only the 
briefest details of this special rocket are recorded, 
since it was not a development of Division 19. More 
thorough treatment is given the launcher and its 
adaption to the firing of Bazooka rounds (Sec- 
tion 1.3.3). 


1.3.1 The Round 3 

The ammunition for which this launcher was de- 
signed was the Navy 3.55-in. SSR. The following 
data apply: 


Length 

Diameter, bourrelets 

W eight 
Payload 

Explosive charge (TNT) 
Maximum velocity 
Fuze 


24.35 in. 


3.500 


-f-0.000 

- 0.010 


in. 


24 lb 
14.6 lb 
1.5 lb 


760 ft per sec 
Nose fuze Mark 


100 Mod. 0 (Su- 
perquick with 
0.05-sec delay) 


Motor burning distance 230 ft at 70 F. 

Firing: electric — through body and the insulated 
contact ring. 

Effective range for this type of use: 1,000 yd or 
less. 

Unavoidable deviation: about 6 mils for moderate 
ranges. 

Lateral deflection for ranges under 1,000 yd: 
about 30 mils left. 


The next to the last datum above is a measure of the 
inherent inaccuracy of the rocket, for rockets do not 
possess the reproducibility of artillery shells. The 
final datum is a deflection inherent in all spin stabi- 
lized rockets and is the result of gyroscopic effects. 

The following examples are quoted to indicate the 
power of the round: with fuze set for 0.05-sec delay, 
the round penetrated a 6. 5-ft thick sandbag target 
and burst on the other side; with a 10-ft thick target 
it burst inside; set for the same delay, a round hitting 


ROCKET LAUNCHER FOR 3.55-INCH SSR 


5 


a 24-in. thick concrete wall burst inside the wall and 
blew out craters 36 to 48 in. both in front and back. 

1.3.2 The Launcher 3 

This was designed to be as light as possible, ex- 
tremely portable, and to serve as container for the 
round and all accessories. Pertinent data are con- 
tained in the following tabulation: 

Weight of launcher with one round and all acces- 
sories: 40 lb. 

Weight of launcher with all accessories: 16 lb. 

Length of launcher including end caps: 32 in. 

Mount: 3 folding legs, the rear spade-shaped, the 
front legs pointed. 

Sight : peep sight with front bead fixed and rear 
peep hole on an arm adjustable for ranges up 
to 1,000 yd. 

Firing: electric, using Navy Mark 22 magneto 
firing key. 

The sight and firing are similar to those of the Ba- 
zooka described in Section 1.2. The launcher was 
made of aluminum alloy for lightness and strength, 
and was treated to resist corrosion. In the complete 
assembly it contained one round, a 25-ft firing line, a 
magneto switch, time Pencils, and trip wire. When 
the legs and sight were folded, the compact unit was 


easily carried on a light packboard, from which it was 
quickly removed and implaced for operation. The de- 
vice was considered as expendable, although it was 
found in actual tests to be capable of firing over 100 
rounds without visible deterioration. 

The sight and elevation adjustments in the legs 
were designed to allow use of the rocket in the inter- 
mediate ranges where its accuracy was good. Such 
ranges corresponded to a reasonably flat trajectory at 
a maximum elevation of 8 degrees, hence the accuracy 
was better against vertical than horizontal targets. 
This was at least equal to the accuracy obtained 
with any launchers from which the 3. 55 -in. rocket 
had been fired. The observed dispersions corre- 
sponded to mean deviations of 6 or 7 mils at the 
ranges tested (apparently a characteristic of the 
round at its state of development). 

1.3.3 Operation 3 

The launcher could be quickly disassembled from 
the pack, and by means of the folding legs set up 
pointing roughly in the correct direction. Final aim 
was secured by elevation and fine traverse adjust- 
ment incorporated in the rear leg mechanism. The 
feet of all three legs were sharp and pointed, so that 
a good hold could be secured in the ground and the 
launcher firmly planted. Even so, it was found neces- 



Figure 2. Launcher assembled with firing line and magneto and round. 


6 


ROCKET LAUNCHERS 



Figure 3. Layout of launcher and round before assembly to packboard. 


sary to weight the launcher to prevent its being upset 
by the blast from the rocket. This was conveniently 
and simply accomplished by including, in the acces- 
sory kit, a canvas and glass cloth bag which was filled 
with about 20 lb of available ballast, such as rock and 
sand, and suspended by a strap passing over the 
launcher tube near the front sight. When the launcher 
was thus weighted, repeated shots could be fired 
without extensive readjustment of the aim. The de- 
tachable rear leg was spade-shaped to assist in ob- 
taining the needed ballast. The rockets were loaded 
and all adjustments were made at the rear end of the 
launcher. 

Firing was accomplished either by trip wire, man- 
ual operation, or by time Pencil. Details of the first 
two of these methods (see Section 1.2) are not in- 
cluded. The time delay firing, however, differed from 
the procedure given in Section 1.2.3, in that the time 
delay Pencil was connected directly to the firing mag- 
neto and the latter was operated by impact of the 
Pencil striker. This change was necessitated by the 
requirement in the case of this rocket of electric 
firing at all times. 

1.3.4 The Bazooka Adapter 4 

It was thought desirable that the launcher for the 
3.55-in. SSR also be able to fire the more readily 
available Bazooka 2.36-in. rockets. Thus the launch- 
er’s usefulness would not cease when the few rounds 
shipped with it to the field had been exhausted. An 
arrangement was worked out consisting primarily of 
three aluminum tubes of such diameter that, when 
inserted into the launcher tube, they provided three 
guiding rails for the smaller round. Three slots at 


each end of the launcher tube served to fix these 
rails in position and their attachment or removal was 
possible in a few seconds. 

The only other special provision was a central 
peep-sight hole (not offset as was the one on the 
launcher which compensated for the lateral drift of 
the SSR) and a spring clip on the ungrounded firing 
contact for attachment to the Bazooka’s firing wire. 


Figure 4. Breech of launcher showing rails and con- 
tacts with 2.36-in. rocket partly inserted; method of 
making electrical contacts with the round; and the two 
peep-sights. 

In actual use with Bazooka rounds, some bad 
yawing occasionally was encountered. This was 
perhaps not unexpected with this rocket 7 and was 
entirely corrected by filling the empty cone of the 
shaped charge with plastic explosive or cast pentolite. 
This, at the same time, increased the charge from 



ROCKET LAUNCHER FOR 3.55-INCH SSR 


7 


0.5 lb to 1.3 lb and gave a range at 8 degrees elevation 
of about 130 yd with good accuracy. It was realized, 
of course, that the penetrating characteristics of the 
original round had been sacrificed and the procedure 
at best was makeshift. Nevertheless, when it is noted 


that the complete modified launcher weighed slightly 
less than the Bazooka launcher, could be operated by 
one man, and could be used to fire rapid and succes- 
sive shots without re-aiming, consideration of this use 
is warranted. 


Chapter 2 

OIL SLICK IGNITER (NO-234) 


2.1 INTRODUCTION 

At the request of the Navy, Division 19 was asked 
to develop a scatter bomb which, when released from 
an airplane traveling at speeds up to 300 mph and at 
altitudes of under 1,000 ft, would reliably ignite 
floating oil slicks. The operational requirement was 
jointly framed by officers in the Bureau of Ordnance, 
the Bureau of Aeronautics, and the Office of the 
Commander in Chief. It was also desired that the oil 
slick igniter be capable of igniting standing pools of 
oil on land, with the oil in either case being devoid of 
volatile constituents. So-called Navy Special, Bunker 
C, and crude oils were accepted as suitable. 

Operationally, it was thought that reconnaissance 
planes equipped with a few igniters of this type would 
be most useful in destroying torpedoed ships and 
tankers floating helplessly on the sea surrounded by 
the oil slick liberated from their opened tanks. The 
land use would be more limited and would be con- 
fined to those rare instances where a large storage 
tank had been ruptured and had released pools of 
standing oil. 

Both problems were met by the development of 
small cardboard cartons containing a fuel charge 
which was ignitable, either by contact with water or 
by a secondary fuze system. The former was known 
as the City Slicker and was either rectangular (CSR) 
or triangular (CST), while the latter, because of its 
function on either sea or land was dubbed Paul Re- 
vere (PR). All are described in this chapter, 9 from 
which it will be seen that the PR differed from the 
CSR only in the addition of the separate fuze system. 

2.2 FUEL CHARGE 1 

Two prior developments by the British were known 
to NDRC workers. These were both primarily of a 
defensive type and had been produced to ignite oil 
slicks which were to be liberated by underwater 
pipes in the face of an attempted invasion of Britain. 
The first of these was the so-called Cough Mixture 
(KOFQR), an alloy of sodium and potassium sus- 
pended in benzene in a frangible glass container. 
This, on impact with the sea, broke, liberating the 
contents which were spontaneously inflammable 
when mixed with water. The other development cen- 
tered on the use of calcium phosphide which was 
similarly employed. 2 * 3 


Neither of these appeared likely to satisfy the 
American offensive requirements, largely because of 
their uncertain behavior against the oils specified, 
and a different igniting charge was therefore ob- 
tained. This charge was based on a product of the 
Permanente Metals Corporation known as Perma- 
nente Mix which closely resembled the standard 
“goop” used in large quantities by the Chemical 
Warfare Service for filling the M-74 and M-76 in- 
cendiary bombs. It consisted of a paste of crude, 
finely divided magnesium (with magnesia and car- 
bon) in Stoddard Solvent-asphalt. This was dried to 
85 per cent + 5 per cent solids, 3.5 per cent ± 0.5 
per cent asphalt, and 11.5 per cent ± 0.5 per cent 
Stoddard Solvent, then screened through a 6-mesh 
0.135-in. screen. The dried solid “goop” thus ob- 
tained contained as a minimum 40 per cent metallic 
magnesium, and was close to the limit of spontaneous 
reaction with moist air. 

Dried iron oxide from mill scale was ground 100 per 
cent through an 80-mesh screen to contain at least 
65 per cent iron and no more than 0.3 per cent mois- 
ture. The dried “goop” was mixed with it in the pro- 
portion of 85 per cent by weight of “goop” and 15 per 
cent iron oxide. In final form the Permanente Mix 
was a dark brown mealy powder, very sensitive to 
water vapor and spontaneously inflammable with 
either salt or fresh water. 

2.3 IGNITION 1 

However, in practice it was found desirable in the 
interest of quick ignition on contact with water, to 
provide a booster. This took the form of a small cloth 
bag of calcium carbide situated in the center of the 
fuel charge and close to the water inlet opening of the 
carton. Penetration of water to the carbide was quick 
and resulted in an immediate and rapid evolution of 
acetylene with attendant heat release which was suf- 
ficient to raise the speed of ignition of the main 
charge to less than 25 sec. This type of ignition sys- 
tem was common to all three devices (CSR, CST, 
PR). 

For land use of PR, a secondary ignition system 
was provided. This consisted of an external celluloid 
case cemented to the side of the carton and communi- 
cating with the main fuel charge by means of an in- 
serted celluloid window. The filling of this case was a 


8 


MANUFACTURE 


9 


hot burning mixture of 88 parts potassium perchlo- 
rate, 11 parts paraffin, and 1 part petroleum coke. 4 
Ignition of this first fire mixture was brought about 
by the action of a time delay Pencil (see Chapter 11) 
equipped with an incendiary matchhead ending. 


2.4 

CONSTRUCTION 

2.4.1 

Of the CST 


The construction of the CST can be seen from 
Figure 1. Because the triangular unit floated on its 
side with either a flat surface or an edge projecting 
a short distance out of the water, the ignition hole 
was placed at the end, in the center. Closure of this 
port (providing for the eventual entrance of water) 
was made with a glued-on brass tear tab having a 
perforation through which a pull ring and string were 
threaded. The tab was not glued directly to the 
carton but to a cardboard ring that could be torn 
without damage to the package wall. 

The carton was provided with a corrugated paper 
liner, inserted with the flukes outward, giving ade- 
quate buoyancy to the packet and contributing to 
the formation of a residual charred shell that sus- 
tained the burning charge in the water and kept it 
from dispersing. Asbestos liners were inserted on all 
three sides between the corrugated liner and the 
carton to prevent the flame from shooting upwards 
and to direct it along the surface of the water and 
hence against the oil slick. The igniter bag contained 
about 25 g of J^-in. calcium carbide wrapped in a 
6-in. square of cheesecloth and a similar square of 
absorbent paper which promoted the absorption of 
water and hence the reaction of the carbide. 

The carton itself was cut by a special die from the 
superior grade of jute board developed for the Quar- 
termaster K-Ration and for Ordnance stores. The 
style of box, with an outside glue flap and a special 
seal, conformed to the best principles of moisture- 
proofed cardboard containers. 

2.4.2 Of the CSR and PR 

Figure 2 illustrates the construction of these more 
elaborate units. The ignition hole, sealed with the 
same brass tear tab used in the CST, was here at the 
center of one of the narrow sides of the rectangular 
package, which floated on one of its wide sides. As- 
bestos liners were provided on the two wide sides to 
direct the flames downward along the surface of the 

Wmm 


water, but there was no asbestos along the narrow 
sides. The corrugated cardboard liner in this case had 
two 1-in. holes which coincided with the two narrow 
sides of the carton. Thus one hole was adjacent to the 
water-admission hole that was covered by the tear 
tab. In the finished munitions, a porous pasteboard 
tube 1-in. in diameter fitted into the two holes pro- 
vided in the corrugated liner, and held a calcium 
carbide igniter-bag in place close to this entrance 
hole. 

In the case of the PR, on the narrow side of the 
carton opposite the tear tab a celluloid case was 
glued to the outer surface. This case contained a cen- 
tral well for inserting a time delay (SRI) and on 
either side of this, chambers filled with the fast burn- 
ing perchlorate mixture already mentioned in Sec- 
tion 2.3. 

2.5 MANUFACTURE 4 

Two semi-production experiences proved the ex- 
treme sensitivity of the igniters to atmospheric hu- 
midity. This difficulty occurred not only in the origi- 
nal production of the fuel charge, the deterioration of 
which could have been foreseen, but also in its subse- 
quent handling during loading procedures and in 
storage, where resistance of the carton to slow mois- 
ture penetration over long periods was small. The 
latter proved a difficult technical problem but was 
eventually solved by using proper glues and by 
lacquering and waxing. This susceptibility on the 
part of the oil slick igniters did not lead to a danger- 
ous condition, rather, duds resulted which while a 
nuisance and certainly undesirable were by no means 
so serious. Nevertheless, with adequate inspection 
during manufacture there is no reason to expect any- 
thing but a perfect product. 

The various steps in manufacture included gluing 
of the sides and ends (and in the case of the PR, affix- 
ing of the celluloid case), which was done in one 
operation using Dewey and Almy adhesive No. 737, 
and drying the freshly glued cartons under weights 
on suitable wooden forms. The hole in the celluloid 
case of the PR, through which the time delay Pencil 
was inserted, was then sealed with a small wad of 
Presstite Fuel Tank Sealer SS-50. 

The dried cartons were then dipped twice in an 
18 per cent solution of vinylite (VMCH resin) in 
hexone (60 parts) and toluene (40 parts) and placed 
to dry on specially made racks in a current of warm 
air for two hours. 


10 


OIL SLICK IGNITER (NO-234) 


Cardboards — 
carton; 

(lacquered inside 
and out with 
Vinylite VMCH) 



Presstite 
sealing compound 


Permanente 
mix 


Cardboard 

ring 


Brass tear tab 



-Wax dipped 


Asbestos liner 

(one each side) 


Corrugated liner 

Lead wire 
Igniter bag; 

(calcium carbide 
wrapped in 
absorbent paper 
and cheesecloth) 



Figure 1 . City Slicker, Triangular. 



MANUFACTURE 


11 


Corrugated 
liner 


Lacquered 

carton 


Brass 
tear tab 


Cardboard 
ring 

Cardboard 
tube 

Permanente 
mix 



Asbestos liner 

(wide sides only) PreSStite 

sealing compound 


Asbestos 


Corrugated XJS 
liner m 


Brass 
tear tab 

Cardboard 
ring 

Carton 



Glued to carton 


/ 

Kraus mixture Celluloid 



Activated 

delay 

pencil 


Asbestos 


Igniter bag 

(calcium carbide 
wrapped in 
absorbent paper) 


Celluloid 

window 


Rubber gasket 

Corrugated spacers 


Trunk lock 



30 (SRI)s in 
6 metal containers 


Steel box 

(with soldered seams) 


Figure 2. The Paul Revere. 




12 


OIL SLICK IGNITER (NO-234) 


The loading had to be done under atmospheric 
conditions which would insure both safety in the 
handling of the Permanente Mix and complete pro- 
tection from any deterioration of either this material 
or the calcium carbide during the very brief period of 
exposure involved. The cartons were inspected for 
any irregularities which might interfere with the 
subsequent sealing operation, and the corrugated 
liners and asbestos liners were inserted, followed by 
the fuel charge and lastly the calcium carbide bag. 
(In loading the PR unit the carton was first filled to 
within about in. of the side holes, the tube con- 
taining the calcium carbide bag was inserted, and the 
filling with Permanente Mix was then completed.) 

The filled cartons were then sealed with Presstite 
Extruded Fuel Tank Sealer SS-50 under pressure, 
painted on the exposed edges with a liberal portion of 
Glyptal Cement No. 1276 and dried with that end up 
for 3 hours. The final operation was to dip each car- 
ton individually in Darex Thermoplastic Coating 
BM16 at 120 C + 5 C. 

The finished units, thus obtained, measured as 
follows: CST: length in., width 3^ in., weight 
0.88 ± 0.06 lb; CSR and PR: length 5% in., breadth 
4 in., thickness 2)^ in., weight 1.16 lb + 0.06 lb. 

It should be noted that the lacquering finish ap- 
plied was impervious to the oils in the fuel charge, 
while the exterior wax coating was impervious to 
water vapor. 

2.6 INSPECTION TESTS 4 

To insure a reliable product and to provide test 
procedures suitable for quality control, it was neces- 
sary to devise simple and routine tests for the use of 
the manufacturer and the Service Procurement 
Office. The test for function was naturally the first 
and most important of these. One per cent of each 
1,000 units was tested in water to meet the specifica- 
tion of positive ignition in less than 25 sec and con- 
tinued burning time of at least 1 min. This was there- 
fore a conclusive test of the finished product but was 
of no value in locating unforeseen troubles before they 
had affected quality. 

More valuable from a practical point of view was 
the so-called Lily cup test. A mixture of 30 g of Per- 
manente Mix, 10 g of 34 - i n - calcium carbide and 
15 cc of water in a paper cup was timed for first ig- 
nition. A fairly accurate estimate of the reactiveness 
of the fuel charge was thereby secured, but an exact 
correlation between the timings given by this test 


and the performance of the igniters in the first test 
was never deduced. 

A third test of great value and simplicity deter- 
mined the extent of deterioration of the calcium car- 
bide in a given igniter. Repeated observation showed 
that any moisture capable of penetrating to the in- 
terior of the carton preferentially attacked the car- 
bide with the result that lumps disintegrated into 
dust. Accurate measurement of this dust was simple 
and indicated the extent of moisture penetration. 
While the amount of carbide present was several 
times the minimum needed, loss of more than 10 per 
cent of that originally present was considered serious 
and an indication that the elaborate waterproofing 
treatment with lacquers and wax was inadequate. 

In the case of the PR units an additional test was 
made to insure the quality of the fast burning mix- 
ture contained in the celluloid case. For this purpose, 
the total burning time of the case and its filling was 
specified to fall within 20 to 30 sec. 

Exhaustive trials were run on the finished units 
under a variety of humidity and temperature ex- 
posures to prove the adequacy of the moisture-proof- 
ing coatings. Of all these, that test in which the indi- 
vidual units were left in a stream of running tap 
water proved the most severe. In the CST, CSR, and 
PR units just described, even this test was passed 
without loss of efficiency after a week’s trial. The 
test as applied in manufacture specified that 1 per 
cent of the production units be floated in pans of 
running water for 48 hours and the carbide and spe- 
cial PR tests described immediately above were then 
made. 

2.7 PACKAGING 

Figures 1 and 2 indicate the way in which the CST 
and PR, or CSR, units were supplied to the field. 
The CST’s were grouped in a hexagon contained in a 
streamlined, cylindrical bomb casing adapted for 
loading on the 100-lb stations of Army or Navy 
planes. The CSR and PR units were packed either 
in rubber gasketed steel boxes, similar to the one il- 
lustrated in Figure 2, or in the cheaper and more 
available 0.50-cal. M2 steel ammunition cases. The 
common feature of all three types of package was 
their watertightness until the moment the incendi- 
aries operated. 

2.8 OPERATION FROM AIRCRAFT 1 

The CST was designed for clustering in the bomb 
case. The details of the construction, operation, and 




OPERATION FROM AIRCRAFT 


13 


Ring^of Presstite seal ing compou nd 


•«d 


-C 




Rubber gasket 



<00f Si0 

Spring/ Guide 

essw***®®® 



Quick opening 
buckle 

Safety wire 


Suspension lugs 



'Wrought 
iron link 


Arming wire 


Woo'd 1 For 
Utilitape J packing 


Wood 


Soldered 
joint 



Figure 3. Quick-opening clusters of 24 City Slickers, Triangular. 





14 


OIL SLICK IGNITER (NO-234) 


packaging of a quick-opening cluster of 24 CSTs 
are shown in Figure 3. These clusters were carefully 
tested several times at the U. S. Naval Proving 
Ground, Dahlgren, Virginia, and found to operate 
satisfactorily and safely. The two sections of the case 
were hinged securely together at the nose to prevent 
initial opening at that point when the bomb was re- 
leased into the airstream. A pair of springs, com- 
pressed into wells drilled in blocks of wood mounted 
in the tail section, forced the sections apart at the 
tail, when withdrawal of the arming wire from the 
buckles allowed the steel straps to open. The 24 
CST’s were packed into the casing in pairs after re- 
moving their tear tabs and cementing the two units 
(with their ignition holes abutting) by Presstite 
Sealer. This temporary seal sufficiently waterproofed 
the units during their brief exposure to air while the 
bomb casing was being loaded. 

On release from a torpedo bomber at altitudes of 
150 to 600 ft and speeds of 175 to 300 knots, the 
clusters opened an average of 40 ft behind the plane 
and 25 ft below it, the individual CST’s or pairs 
spread out in the airstream behind the plane and 
gave pattern areas roughly as shown in Table 1. 


Table 1 . Results of release of CST’s from torpedo 
bomber. 


Altitude of release 

Diameter of pattern 

600 ft 

150 ft 

450 ft 

80 ft 

175 ft 

60 ft 


CST’s so released withstood the impact on water 
very well and functioning was well over 80 per cent 
with normal burning. 

Another use for the CST that seemed even more 
attractive was as a munition of opportunity to be 
carried by aircraft operating over water. Release was 
by hand in a cluster of six units bound loosely to- 
gether with tape, as illustrated in Figure 1. Just 
prior to release from the plane the rip cord could be 
pulled, tearing off all the tabs and readying the units 
for instant operation on contact with water. These 
clusters of six fell through the air as a unit, which on 
striking the water broke apart scattering the indi- 
vidual igniters over an oblong area. There was some 
skipping, with the units coming to final rest about 
30 yd ahead of the point of original impact. 


Probably the PR would be useful in a similar oper- 
ation. As already stated it has the added features of 
delayed action (either on land or water) and of oper- 
ation on land, features which might recommend it in 
some special operations. Needless to say, all types of 
oil slick igniters could be used by individual foot 
soldiers and thrown into slicks by hand, and, be- 
cause of demonstrated reliability, a single unit or 
perhaps a pair should suffice for a given target. 

2.9 PERFORMANCE 

Earlier work 5 cast some doubt on the practicabil- 
ity of igniting bodies of floating oil, it being noted 
that ignition of films of less than 0.1-in. thickness was 
impossible. There was some question also whether 
crude and heavy oils such as Diesel and Bunker C, 
from which all volatiles had been stripped, could be 
ignited at all in large bodies. Also, it appeared that 
waves, wind, and passing ships could be expected to 
produce an oil-water emulsion which would not burn 
under any conditions. 

These doubts were settled by many tests under a 
variety of temperature and wind conditions. It was 
thus definitely established that films over 0.1 in. in 
thickness could be reliably ignited by the extremelj r 
hot flame of the CST or PR. Because of the con- 
sistent performance of the igniters, the scattered pat- 
tern expected on jettisoning from a plane, and the 
size of the slicks encountered in the field, it seemed 
reasonable to assume their function from a single 
large-scale demonstration. This was arranged by offi- 
cers assigned to OSS and took place on the New 
Jersey shore in June 1944 when 1,000 gal of Navy 
special fuel oil was ignited by the action of a single 
CST in less than 4 min. 6 The fire burned into the 
wind with flames billowing to a height of 50 ft and 
lasted for 7 min. As in all cases, there remained after- 
wards a considerable unburned tarry residue floating 
on the surface. 

This large trial was of course preceded by many 
small trials and demonstrations performed by the 
contractor and the division’s central laboratory. 7 In 
all these, as well as in the large trial, the units were 
thrown in by hand, and it was independently shown 
that their functioning was unimpaired when thrown 
from aircraft. 8 


Chapter 3 

GRENADE, HAND, FRAGMENTATION, T-13 (BEANO) 


3.1 INTRODUCTION 

The work of Division 19 in the field of impact hand 
grenades had its origin in a request received from the 
Research and Development Division of OSS on their 
own behalf and with the support of the Grenade Sec- 
tion of the Ammunition Division of the Army Ord- 
nance Department. As the development proceeded, 
contacts in the Army included the Army Ground 
Forces, and in the Navy, the Marine Forces, both of 
these groups being the branches using such a weapon. 
Upon withdrawal of the division from the problem 
in June 1945, the grenade became the exclusive 
charge of the Ordnance Department, which contin- 
ued experimental and developmental work. No 
formal problem request was ever received from the 
Army or Navy in distinction to OSS. 

The ideas underlying Beano 128 were not original : it 
had been frequently suggested previously by respon- 
sible individuals that first an improvement in the 
standard existing U. S. Army fragmentation grenade 
was needed; that, secondly, an impact type of gre- 
nade would be a desirable adjunct to the Army’s 
munitions ; and that, thirdly, a grenade based on the 
size and shape of a baseball would be better adapted 
to use by the average American soldier than was the 
heavy pineapple-shaped Mark II. The poor perform- 
ance of the latter, which gave rise to that opinion, 
was later greatly improved by the substitution of 
2.05 oz of cast TNT for the previously used filling of 
0.74 oz of E.C. nitrocellulose powder. 

A combination of the above three guiding princi- 
ples led to the development of Beano, although vari- 
ous other requirements were included in the state- 
ment of the problem as well. These included specifi- 
cations regarding sensitivity to impact, a dual arming 
system with the second arming operation occurring 
after the grenade left the thrower’s hand, and the 
usual requirements of waterproofness, shock resist- 
ance and safety to the user. The fulfillment of all 
these points to the satisfaction of the Ordnance De- 
partment was not accomplished in the time available, 
but was very nearly achieved. Whether it was so 
nearly achieved during the active days of World War 
Has to have warranted field use is a matter of opinion. 
At least it can be said that Beano should be a valuable 
weapon in any future wars and a most useful adjunct 


to the now improved Mark II grenade which it com- 
plements in many respects. 

3 . 1.1 Exact Requirements 

The characteristics, suggested and implied, of this 
grenade were : (1) It should be the same size and shape 
as a baseball (a sphere 93^ in. in circumference). 

(2) It should approximate its weight. As shown in 
Section 3.2, this was eventually fixed at 11 ± 1 oz. 

(3) It should fire on impact rather than by time delay 
as did the Mark II, which employed a Bouchon fuze 
of approximately 4.5-sec delay. (4) It should fire re- 
liably when dropped 18 in. onto sponge rubber. This 
measure of the sensitivity was later modified to a 
12-in. drop equatorially onto concrete. (5) It should 
be spherically balanced, a requirement which was ap- 
proximated in the first model of the fuze T-5 but 
more exactly met in the final model T-5E3. (6) It 
should have “optimum lethal fragmentation.” Just 
what this meant was a matter of personal interpre- 
tation, since there is no satisfactory criterion of le- 
thality of particles which connects size, mass, and ve- 
locity with personal injury regardless of the part of 
the anatomy struck. Some discussion of this point 
will be found in Section 3.5.3. (7) It should have two 
arming mechanisms, the second to take place during 
flight. This seemingly difficult specification was met 
most satisfactorily by the so-called butterfly (see 
Section 3.4.3). (8) It should be waterproof, capable 
of withstanding the Army Ordnance Jolt and Jumble 
Test, and its safety and operation should be unaf- 
fected by rough handling and severe weathering. 

3.2 DETERMINATION OF ALLOWABLE 
WEIGHT 3 

The original hope that Beano might not only have 
the same size as a baseball but also the same weight 
(5)^ oz) was doomed at the outset by the required 
ratio of weight of high explosive filling to weight of 
case, which provided the lethal fragments. Either the 
explosive charge would have to be diminished and 
the case made of very light material or else the over- 
all weight of the grenade would have to be signifi- 
cantly increased to over 53^ oz. The latter course 
was adopted and the specification (2) above was 


16 


GRENADE, HAND, FRAGMENTATION, T-13 (BEANO) 


established. The figure of 11 ± 1 oz was derived 
after several series of trials in which soldiers were 
provided with a variety of spheres, cubes, and cylin- 
ders of wood variously weighted and, in repeated 
throwing trials, judged for accuracy, range, and en- 
durance. The original studies indicated that 12 oz 
would be the point of maximum efficiency, 3a a deci- 
sion which, by coincidence, just sufficed to cover the 
optimum weights of the fuze body, the fragmenta- 
tion casing, and the explosive filling. 

Later studies showed 3b that the average obtain- 
able range increased about 1 yd (out of approxi- 
mately 45 yd) for each decrease of 1 oz in weight. 
See Table 1. 


Table 1 . Summary of throws for distance. 


Weight 

No. throws 

Arithmetic 
means of distances 

12 oz 

309 

47.5 yd 

14 oz 

309 

46.1 yd 

16 oz 

309 

43.5 yd 

18 oz 

309 

42.4 yd 


The information on accuracy was more difficult to 
analyze and only led to the generalization that, bar- 
ring fatigue and figuring the accuracy of each throw 
as the maximum distance readily attained with a 
given weight, there appeared to be no significant 
change in accuracy with change in weight. All throws 
were made overhand in contrast to the side and un- 
derhand technique usually employed with the 22-oz 
Mark II. 

3.3 SELECTION OF CASE 7 

Extensive trials of a number of metals including 
steel of several thicknesses, aluminum, and mag- 
nesium showed at once that, if anything more than 
a blast effect were desired of Beano, a steel case was 
definitely needed. 5 This was true regardless of the 
type of explosive filling employed. 

Table 2 shows very clearly the preference for steel 
to aluminum (a similar table for magnesium could be 
presented) and at the same time indicates the value 
of a filling more dense than TNT at 0.80. A slight 
preference would also seem to be indicated for a longi- 
tudinal rather than an equatorial weld. This was not 
sufficiently clear, however, to warrant the additional 
complication entailed in manufacture. 

A choice of case thickness was made in favor of 
0.040-in. steel because of greater ease in manufacture 
and because of the greater density of fragments, 
which were admittedly lighter and of shorter range. 


Table 2. Summary of fragmentation studies of ex- 
perimental spherical grenade cases. 


Case 

and 

Weld 

Wall 

thickness 

inches 

Charge 

Density 

Results 
46^" belt of 
1" pine at 85" 
No. throws 
per sq ft 

Steel 

Equatorial 

0.040 

TNT 

0.80 

0.686 

Steel 

Longitudinal 

0.040 

TNT 

0.80 

0.850 

Steel 

Equatorial 

0.060 

TNT 

0.80 

0.622 

Steel 

Equatorial 

0.040 

Cast 

Pentolite 

1.62 

1.14 

Aluminum 

Equatorial 

0.095 

TNT 

0.80 

0.262 

Aluminum 

Equatorial 

0.135 

TNT 

0.80 

0.262 


It is convenient to express the performance charac- 
teristics of a Beano by giving the range at which the 
density of perforating particles averages 0.35 per 
sq ft, a the average linear dimension of the holes per- 
forated, and the average weight of the perforating 
fragments. These data are given for the two weights 
of steel cases in Table 3 and show a slight preference 
for the 0.040-in. case which was used in all production 
models. 


Table 3. Performance characteristics of Beano. 



HE charge- 

Range to 

Average 

Average 


case ratio 

d-35 

dimension 

weight 

0.040 Steel 

1.07 

10.0 ft 

0.31" 

0.30 g 

0.060 Steel 

0.59 

7.8 

0.45 

0.56 


(Similar data could be included which would indi- 
cate that the fuze assembly used in conjunction with 
this case would give better fragmentation, if made of 
aluminum rather than the bakelite actually employed 
in all but the T-5E2 and T-5E3 production. 7 ) 

Selection of the proper filling of high explosive for 
this case narrowed to a choice between TNT and 
RDX (Composition A) after the exclusion of am- 
monium picrate and cast pentolite. The choice be- 
tween the two remaining explosives was finally made 
by the Services in favor of the latter on the basis of 
evidence such as that shown 11 in Table 4. Although 
the total area of penetration was about the same in 
all these cases, the number of particles was much 


a When the fragment density is 0.35 or greater, a man, on 
the average, will be struck in other than a trivial region by 
one or more fragments. 7 


DEVELOPMENT OF THE FUZE T-5 


17 


larger in the case of Composition A (although the 
average weight of each was correspondingly smaller), 
and Composition A was preferred. 

Table 4. Comparison of TNT & Composition A fillings. 


Charge 

Density 

Booster 

No. 

throws* 

TNT 

0.8 

2.34 g tetryl 

106 

TNT + beeswax 

0.87 + 7% 
beeswax 

2.34 g tetryl 

56 

TNT 

0.87 

8 g tetryl 

117 

Composition A 

0.93 

2.34 g tetryl 

281 


* (Cf. Table 2) 


The case in final form may now be described as 
consisting of two stampings of 0.040-in. steel, copper 
brazed at the equator. One stamping had an opening 
to receive the fuze and was provided with the brazed 
threaded insert holding the aluminum former cup. 
Filling was by either Composition A with a density 
of 0.93, which gave a total weight to the grenade of 
11.9 oz, or by granular TNT with a density of 0.8, 
which gave a total weight to the grenade of 11.3 oz. 
The volume available for high explosive filling was 
140 cc, and this allowed the use of 4.6 oz of Compo- 
sition A or 4.0 oz of TNT. The outside diameter of 
the case was 2% in. at the equator. The weight of the 
empty case assembly, including the aluminum former 
cup and its brass retaining ring was 4.8 oz. 

3.4 DEVELOPMENT OF THE FUZE T-5 15 

3.4.1 Origin of Design 

The division was indebted primarily to the British 
for several design features of the impact fuze. This 
was because of the large scale production for the 
British Army, both in the United Kingdom and in 
Canada, of their standard grenade No. 69 Mk. 1 
which was equipped with an impact type bakelite 
fuze. British reports and suggestions 2 - 4 used by 
Division 19 research workers gave valuable assist- 
ance, especially in locating pitfalls to be avoided. 
The fuze T-5 which finally resulted is shown in cross 
section in Figure 1. 

A comparison of the T-5 with British fuze shows a 
difference. The secondary arming pin, attached by 
nylon string to the butterfly cap, in the American 
design entered the firing pin mount vertically and 
gave safety by holding apart two small steel balls, 
which engaged the shoulder of the primer mount. In 
the British fuze No. 247 this pin entered at an angle, 



there were no balls, and it was possible to throw the 
grenade in such a way that arming in flight could not 
occur. Another significant change was in the elimina- 
tion in the T-5 of one of the conical surfaces on which 
the inertia parts of the fuze moved at the moment of 
impact. This insured a better alignment of the primer 
and the detonator at the moment of firing. 15a 

3.4.2 Assembly and Description 

Figure 2 shows the T-13 grenade with its case and 
T-5 fuze disassembled. The fuze itself was composed 
of a number of metal and two bakelite parts, the fuze 
head and the fuze body. The fuze head was equipped 
with threads to screw into the grenade and to receive 
the fuze body. On one side it was provided with a 
smooth cam surface with a central opening through 
which passed the secondary arming pin. On the other 
side it was provided with a brass-inserted spool 
around which a Nylon thread was wound connecting 
the secondary arming pin with an aluminum butter- 
fly cap, which up to the moment of use was held in 
place by the arming pin (a ring-pulled type sup- 
ported by two ears provided in the bakelite casting). 
The body of the fuze was roughly conical in shape 
and had a flat inner surface on which the fuze parts 
rested. This was penetrated by a hole, which in as- 
sembly received the detonator. The bottom end of 
the bakelite part was threaded to accommodate an 
aluminum cup, which in assembly contained a felt 


18 


GRENADE, HAND, FRAGMENTATION, T-13 (BEANO) 



Figure 2. Disassembled view of T-13 grenade and T-5 
fuze. 


pad and two tetryl pellets constituting the burster 
insuring high order detonation. The metal fuze parts 
which operated inside the bakelite housing consisted 
of a brass primer mount and a brass plunger. The 
primer mount, which rested upon the flat inner bot- 
tom surface of the fuze body, was provided with a 
cavity, in which the primer was mounted. A steel fir- 
ing pin was an integral part of the heavy brass 
plunger which moved smoothly inside the primer 
mount without actual contact between the firing pin 
and the exposed primer because of a weak creep 
spring. 

The butterfly was cast aluminum with cross rib- 
bing to provide a good finger grip. It was connected 
to the secondary safety pin by 6 in. of 30-lb nylon 
line. The radius of the dome or cam and its position 
relative to the fuze body were dimensionally impor- 
tant. On the basis of British work this interior angle 
was as close to 115 degrees as possible. The strength 
of the creep spring was an adjustable feature which 
determined the sensitivity of the grenade; it con- 
sisted of 6 coils of 0.010-in. diam tinned music wire 
with open-end winding. The sharpness and angle of 
the firing pin was also vital; it was necessary that 
the angle be less than 0.010-in. flat. 6 

The initiating system 15a consisted of the M26 
primer, the M17 detonator, and a tetryl burster. 
This train was selected because it represented the 


maximum sensitivity obtainable in standard items. 
The M26 primer was the suggestion of Picatinny 
Arsenal. It contained 2.05 grains of 40-35-25 mer- 
cury fulminate — potassium chlorate — antimony 
sulfide pressed at 20,000 lb per sq in. The charge was 
contained in a gilded metal cup covered with an 
0.0012-in. gilding metal disk sealed with waterproof 
wax. The primer was of the stab type. The deto- 
nator, also recommended by Picatinny Arsenal, was 
the M17 and contained a primary charge of 3.86 
grains of lead azide pressed at 10,000 lb per sq in. 
and a booster charge of approximately 1.27 grains of 
tetryl containing a maximum of 2 per cent graphite. 
The burster consisted of two pellets of tetryl roughly 
% in. by 34 in. with a density of 1.49. Their total 
weight was 5 g, which was approximately twice the 
minimum. This assured satisfactory performance re- 
gardless of the explosive used in the case. 

3.4.3 Arming and Operation 

In the unarmed condition the grenade was ren- 
dered safe by the intrusion, into the upper part of the 
firing pin mount, of the secondary safety pin, which 
penetrated the bakelite cam surface centrally. While 
this safety pin was in position in the firing pin mount, 
it held apart two steel balls which protruded beyond 
the edge of the primer mount and effectively kept the 
fuze parts from movement. Upon the withdrawal of 
the secondary arming pin, the steel balls no longer 
performed this function and the brass fuze parts were 
free to move within the bakelite fuze body. Any sub- 
stantial deceleration of the grenade in this condition, 
regardless of direction, resulted in movement of the 
firing pin mount, within the primer mount, against 
the creep spring with resultant piercing of the primer, 
passage of the resulting spit into the detonator, and 
thus in explosion of the grenade. 

When the grenade was thrown after removal of the 
safety pin, the cap was forced away from the fuze 
body by a cap spring and acted as a parachute, un- 
winding the nylon string and pulling out the arming 
pin while the grenade was in flight. With an average 
throw, arming occurred at a distance of about 20 ft. 

3.5 PERFORMANCE 

3.5.1 Sensitivity 

Probably the most significant quality of any im- 
pact fuze is its sensitivity. In the present case it was 
desired that a fuze be made which would fire reliably 



PERFORMANCE 


19 


on striking any solid surface with the force ordinarily 
supplied by an average thrower or by gravity from a 
reasonable height. This indicated a fuze of consider- 
able sensitivity, and, at the same time it was clear 
that the fuze should not be so sensitive as to be an 
unusual hazard in assembly or in correct usage. The 
exact requirement finally framed [see (4) under Sec- 
tion 3.1.1] was meant to represent the best compro- 
mise between these opposite demands. It will be seen 
at once that it did not correspond to the extremely 
variable field conditions certain to be encountered. 

The most valuable data on the subject was ac- 
quired by the Army Ground Forces in exhaustive 
tests conducted by the Infantry Board at Fort Ben- 
ning, Georgia. 21 Using live, as well as dummy, gre- 
nades and Army personnel, these tests made it clear 
that the percentage of malfunctioning caused by dif- 
ferences in targets was greatly affected by the tech- 
nique used in throwing. Flat trajectories resulting in 
a glancing impact produced a relatively high per- 
centage of malfunctions which increased rapidly with 
the softness and resiliency of the impact area. On 
targets of the latter type a high, arched trajectory 
was found essential to give reliable performance and 
even so, in exceptionally soft mud, water, or freshly 
fallen snow, 25 duds averaging 9 per cent could not be 
avoided. This defect had to be accepted as inherent 
in the design and represented a danger in the use of 
Beano by troops operating offensively under such 
terrain conditions. Presumably, the perfect impact 
grenade would be equipped with a secondary time 
delay firing system which would dispose of these duds 
after an interval of several seconds. Such a design 
was at times discussed but, in the time allotted, could 
not feasibly be developed. 

3.5.2 Fragmentation 

Many independent fragmentation tests were con- 
ducted by NDRC, 71112 Army Ground Forces and 
chiefly by the Ordnance Department 22 at Aberdeen 9 
and Picatinny, 14 with generally good agreement. The 
standard Ordnance test procedure was employed, in 
which the total number of perforations was counted 
in two facing semicircles of 1 in. No. 2 sugar pine of 
10 to 20 ft diameter and 6 ft height. 8 When the gre- 
nade was fired in horizontal position, the fuze axis 
was in line with the common diameter of the targets 
and at mid height. Panel perforations were accepted 
as the significant criterion. 

Table 5 presents some interesting data of this 
type. 8, 22> 24 


The figures in Table 5 indicate the continued im- 
provement in the functioning of the Mark II grenade 
as the fuze and filling were altered. They indicate 
also that Beano was closer to an offensive type gre- 
nade, since stray particles did not fly to great dis- 
tances, and that Beano’s efficiency at close range was 
nearty twice that of the standard grenade — a fea- 
ture which is important when it is realized that 
Beano could be more accurately thrown over all 
ranges because of its smaller weight (11.5 oz vs 21 oz) 
and more convenient size and shape. 


Table 5. 


Horizontal position 

Average number 
perforations 
for semicircles 

Type 

Load 

Fuze 

10' 

20' 

40' 

80' 

Mk II 

0.74 oz E.C. 

M10A2 

5 

2.2 



Mk II 

0.74 oz E.C. 

M6A3E1 

19 

9.5 



Mk II 

2.05 oz TNT 

M6A3E1 

25.5 

16.0 

9.6 

2.0 

T-13 

4.0 oz TNT 

T-5 

22.8 

6.0 



T-13 

4.6 oz Comp. A 

T-5 

50.2 

12.0 

1.2 

0.0 


The velocity of the Beano fragments averaged 
4,100 with TNT loading and 4,900 ft per sec with 
Composition A filling. 9 

A table similar to Table 5 with the grenades placed 
vertically would show the difference in performance 
between the last Mark II type and Beano to be small 
and slightly in favor of the Mark II at the closer 
ranges. The two were therefore comparable in frag- 
mentation at 10 and 20 ft, but beyond that the 
Beano fragments very quickly lost their momentum, 
thus making the grenade safer to the user with less 
need for protection. 

3.5.3 Lethality 

Since this was the object of developing the grenade, 
some judgment must be given on the performance of 
Beano on this score, even while it is realized that an 
exact criterion is not possible. Excellent attempts of 
this type have been made however, of which two ap- 
pear most significant. 18 From these it would seem 
that the perforation measurement used in Table 5 
may not be a true appraisal of lethality or incapaci- 
tation. The tremendous number of particles, many 
of which are very small (about 0.0025 oz), flying at 
these very high velocities can be counted on to de- 
liver the maximum casualty producing hits per unit 
area, the closer the target is to the exploding gre- 


20 


GRENADE, HAND, FRAGMENTATION, T-13 (BEANO) 


nade. These interpretations reinforce those given in 
the preceding section that Beano would find its chief 
usefulness as an offensive grenade. At the same time, 
analysis of the data already presented would tend to 
show that, at the range of 20 yd, all types of Mark II 
and Beano are approximately equivalent, with Beano 
more effective at shorter ranges, and the Mark II at 
longer ones. 

The whole argument presented may be upset by 
the entirely unpredictable effect of clothing, which in 
quantity and location is an uncontrollable variable 
affecting the results obtained from all grenades. 13 Just 
what this effect would be in a given shot would be 
impossible to say, but it seems safe to predict that 
clothing would more seriously affect the smaller par- 
ticles of Beano than the larger and more massive 
ones emitted by the Mark II. 

3.6 PRODUCTION 1 

Although in principle the Beano fuze appears sim- 
ple, its manufacture in tremendous quantities was 
attended by more than the usual quality control dif- 
ficulties. These were centered almost entirely in the 
T-5 fuze and its successors, each of which was intro- 
duced to correct some fault in the preceding design. 
The final fuze made during NDRC participation, the 
T5E3, came close to meeting all the previous objec- 
tions and proved easier to manufacture. As an assist- 
ance to the manufacturer and a guide in maintaining 
the quality in full production which had proved ade- 
quate in the semiproduction, Tentative Acceptance 
Requirements 20 were drawn. These were based on 
Ordnance results in the rough-handling, weathering, 
and Jolt and Jumble tests, 10 the behavior on long 
storage, 14 exposure to tropical organisms, 16 and simi- 
lar information. Even so, the original requirements 
were altered on several occasions by common con- 
sent, and, before the final closing of the assembly 
lines (after V-J day), a variety of special tests and 
more conventional production control tests had been 
standardized and had proved their worth. 1 

These tests were primarily concerned with safety 
of the fully assembled grenade and the partially 
armed grenade on accidental dropping and on throw- 
ing. Other features of course were tested, such as 
waterproof ness and reliability of function. The re- 
sults of many thousands of tests of this type will be 
found in the final report of the contractor. 1 

The safe packaging of the loaded grenades for de- 
livery to the field offered difficulties which were, how- 
ever, fully met by the Ordnance development of a 


satisfactory container and the adoption of the prac- 
tice of shipping the fuzes and the bodies disassem- 
bled from each other to avoid simultaneous detona- 
tion of a whole box upon the accidental firing of a 
single grenade. 17 

3.7 MODIFICATION OF THE FUZE T-5 

3.7.1 Need for Improvement 

Although several thousand Beanos had been pro- 
duced and tested by NDRC without a single mishap, 
the early Ordnance production, in an unexplained 
accident, caused a fatality in testing personnel at 
Aberdeen. 22 At once the fuze design was reopened and 
two modifications were forthcoming, the T5E1 and 
the T5E2. The latter represented a significant im- 
provement in the safety of the fuze and differed from 
the T-5 and T5E1 in that the steel balls in the firing 
pin mount were omitted and that the brass piece was 
slotted to receive a steel key, the shoulder of which, 
resting on the primer mount, rendered the grenade 
safe when the arming pin was in place. Removal of 
that pin, however, allowed the key to slip into the 
firing pin mount and to position its sharpened tip 
directly over the primer cap which it pierced when 
the fuze functioned. The details are shown in Fig- 
ure 3. 



MODIFICATION OF THE FUZE T-5 


21 


With the firing pin a part of the key, it was im- 
possible to have a premature firing because of faulty 
or incomplete assembly of parts, a serious defect in 
the T-5 fuze which, it was supposed, might have 
caused prematures, and did require their reworking. 23 

After satisfactory tests of the new design 26 but be- 
fore the T5E2 was released, further accidents with 
the T-5 occurred in the field. These were never com- 
pletely explained. They resulted from the develop- 
mental point of view in a further improved grenade 
in which the case was slightly altered in dimensions 
(T13E1) to permit the fuze to seat itself more deeply 


in the body, thus eliminating its bulgy appearance 
and correcting a slight non-coincidence in the center 
of gravities of the fuze parts and the grenade. It was 
supposed that by centrifugal force this could result in 
premature firing near the thrower’s hand. It was in- 
deed demonstrated 1 that at 1,800 rpm a T-5 fuze 
would fire from this cause, but no thrower in actual 
tests was ever able to hurl a Beano with more than 
1,200 rpm. 

At the same time, the nylon thread connecting the 
butterfly with the arming pin was shortened to pre- 
vent the butterfly from striking the spinning grenade 



22 


GRENADE, HAND, FRAGMENTATION, T-13 (BEANO) 


in mid air when the pin was withdrawn, thus con- 
ceivably giving sufficient lateral movement to fire the 
fuze — a happening which was never demonstrated 
to occur. 1 

The T5E3 fuze was also supplied with a long 
bouchon-type level handle so that the user would 
have his hand over the butterfly when he threw the 
grenade. This point was corrected after the Ordnance 
at Aberdeen discovered that the Beano could be con- 
sistently prematured in the thrower’s hand if, con- 
trary to the instructions, he did not retain his hold 
over this part. 24 

The details of the final design with these modifica- 
tions are seen in Figure 4 of the T13E1 grenade with 
the T5E3 fuze. 

3.8 MODIFICATIONS OF BEANO 

3.8.1 White Phosphorus Loading 

White phosphorus loading is discussed in Chap- 
ter 4 of Part I of this volume. 

3.8.2 Concussion Loading 27 

At the suggestion of officers in Army Ground 
Forces, a preliminary study was made of the per- 
formance of Beano bodies filled with flash powders 
developed by Section 11.2 of NDRC. It was believed 
that the concussion blast might be effective, without 
accompanying shrapnel at close range, and that at 
night the intense flash would blind the enemy for a 
crucial period of many seconds. The cursory tests 
performed indicated that the idea was well-based, 
but, because of the termination of hostilities, it was 
never fully developed. It appeared that one of the 
aluminum cases used in the WP Beano (Chapter 4) 
when filled with a composition of 200-mesh potassium 
perchlorate (60.0 per cent) and PXS-885 50-50 alu- 
minum potassium alloy (40.0 per cent) gave the best 


results. The filling had a total weight of 160 g and 
was dispersed and detonated by the standard Beano 
fuze in which the usual tetryl bursting charge was 
replaced by one of 2.5 g of black powder. 

3.8.3 Time Delay Fuze 19 

Although the impact fuze of Beano was its chief 
novelty, officers in Army Ground Forces believed 
that the grenade would have greater general useful- 
ness, if it could be supplied on occasion with a time 
delay fuze which would be interchangeable in the 
Beano case with the impact fuze. Two models based 
on both the T5 and the T5E2 fuze designs were pro- 
duced in very limited quantity. In each case, the 
secondary arming pin was integral with the butter- 
fly, and, when the grenade left the hand of the 
thrower, the butterfly and the arming pin were 
ejected by a strong underlying spring, with the result 
that the firing pin, which was also under spring ten- 
sion, stabbed an initiating system and began a pyro- 
technic delay. This delay column was % in. in length 
and provided an elapsed time of approximately 
4J^ sec. It consisted of a primer of 70-20-10 antimony 
sulfide — lead thiocyanate — potassium chlorate, a 
delay powder of 85-15 barium oxide — selenium with 
added talc, and a standard detonator of lead azide. 

3.9 CONCLUSION 

The division personnel regret that a spherical im- 
pact grenade, fulfilling the requirements of safety 
and effectiveness determined by the Ordnance De- 
partment, was not produced to meet the large needs 
of the Ground Forces. It is hoped that its work, how- 
ever, will stimulate future developers to successful 
production of a weapon of this type which will un- 
doubtedly be a valuable complement to the standard 
improved Mark II grenade. 




Chapter 4 


WP BEANO (OD-176) 


4.1 INTRODUCTION 

It was the desire of liaison officers in the Army 
Ground Forces that several modifications of the origi- 
nal Beano be developed for production and use fol- 
lowing the hoped-for adoption of the impact, frag- 
mentation hand grenade as a general weapon. Two 
of these, the Concussion Beano and the Time Delay 
Beano, have already been mentioned. A third, a 
modification in which the loading was white phos- 
phorus (WP), is described in this chapter. The de- 
velopment was requested by the Ordnance Depart- 
ment (OD-176) and closely followed by OD and the 
Chemical Warfare Service, without whose interest 
and assistance an entirely satisfactory solution would 
not have been forthcoming. 

It was decided, as a working hypothesis, that the 
WP Beano {grenade, hand, smoke, WP T-28 and its 
accompanying fuze T-21) should have the same di- 
mensions and weight as the standard high explosive 
grenade T-13 and should use so far as possible the 
same fuze T-5, altered only in those details imposed 
by the new requirements. A decision, similar to the 
one made in the case of Beano, was required, in 
which a compromise was made between the danger 
and the effectiveness of dispersion. 9 - 11 Ultimately a 
compromise was made between the antipersonnel 
features of WP and the economical and efficient 
utilization of the volume and weight of WP available 
within the space of a Beano casing. A bursting charge 
of tetryl would eject particles of WP, 34 to J4 in. in 
diameter, these being judged sufficient to incapaci- 
tate and yet sufficiently numerous to strike a target 
at ranges up to 20 yd. 

The result of these considerations was the com- 
plete development and semi-production of a grenade, 
which appeared satisfactory in limited NDRC test- 
ing but which was never completely tested by service 
boards because of design troubles with the T-5 fuze 
(see Section 3.7). At the time when the division 
terminated its activity, however, it had shown that 
aluminum was suitable for a body case, that it was 
compatible with WP, that its strength and lightness 
made it practically unique as a satisfactory material, 
and that WP was superior to similar fillings (PWP 
and SWP) for such use. 


4.2 THE CASE T-28 2 

4.2.1 Unsuccessful Attempts 

Cases made from steel, brass, copper, ethylcellu- 
lose, and aluminum were tested. Of these, only alumi- 
num cases proved satisfactory, but the others de- 
serve some mention. The case construction of the 
T-13 (Section 3.3.3) naturally suggested steel, which 
was ordinarily used in WP munitions, but which for 
two reasons seemed unsuitable here. First, there was 
the rigid requirement that no leakage should appear at 
temperatures from —50 to +150 F even after rough 
handling, and, secondly, there was an unfavorable 
weight relationship which would not permit a large 
enough charge of WP to be useful. In regard to leak- 
age, it must be remembered that only a thin gauge 
metal, an involved form difficult to seal, was possible; 
the overall weight of the WP grenade was held the 
same as the high explosive (11 + 1 oz), while the 
density of the filling had increased from 0.93 to 1.82. 

Using the standard case design with the T-13, but 
changing the steel thickness to 0.020 in., the lowest 
feasible point, and providing a seal of Dewey and 
Almy No. 200 can-sealing compound between the 
underside of the lip of the aluminum former cup and 
the inner edge of the steel hemisphere, a case was 
obtained which survived moderately rough treat- 
ment, but not prolonged storage. 5 This basic design 
is illustrated in Figure 1. 

The standard Beano case of 0.040-in. steel of this 
design was so heavy that the payload was too small, 
and, furthermore, the tetryl burster charge required 
to open this heavy case was so large that it com- 
pletely shattered the small WP charge and produced 
only harmless smoke. The 0.020-in. steel case, while 
without this defect, fragmented unevenly, yielded 
first at the hemispherical welded seam, exerting a 
marked and unpredictable directional effect on the 
burst, and failed to eject the full WP load. Similar 
results were obtained with identical brass and copper 
designs, and it appeared that a uniform case of 
weaker and lighter composition was necessary. 

Two attempts using blown ethylcellulose 3 and 
aluminum (0.036 in. 2S alloy), both of the same 


Restricted J 


23 


24 


WP BEANO (OD-176) 



design shown in Figure 1, showed conclusively that a 
step forward had been taken. More uniform distri- 
bution of WP particles resulted, and a significantly 
improved payload was obtained. Nevertheless, the 
inherent weakness of the design was apparent, be- 
cause leakage and uneven fragmentation of the case 
still occurred. A second design was therefore indi- 
cated and experimental sample orders of the type 
shown in Figure 2 were tested in the most promising 
materials, ethy]cellulose and aluminum. The latter is 
shown in cross section. Like the units shown in Fig- 
ure 1, these cases required a much smaller bursting 
charge of tetryl than the standard T-13, gave more 



Figure 2. 0.036 aluminum WP Beano case. 


uniform performance and improved efficiency, and 
corrected the weaknesses of the earlier design. 

A choice between ethylcellulose and aluminum 
was not difficult to make, for the former was shown 
conclusively to be incapable of surviving the rigorous 
Jolt and Jumble Test of Army Ordnance as well as 
the weathering and surveillance tests required by 
CWS. In addition, the plastic unit was combustible, 
a most undesirable feature in a container of a spon- 
taneously combustible material such as WP. There- 
fore an aluminum body of the design shown in Fig- 
ure 2, 9 was chosen. 

Table 1 gives the pertinent data for these various 
models. 

4.2.2 The Final Design 

The production body was made of five parts, all 
aluminum: two stampings, a fuze ring, a filler bush- 
ing, and a sealing plug. The stamping, which incor- 
porated the fuze former cup, was the result of very 
excellent technique on the part of the semi-pro- 
ducer. 12 The hemispherical stamping, which carried 
the filling port, was more conventional. Both were 
made from Alcoa No. 21 brazing sheet (heat treatable 
and 0.032 in. thick). The alloy consisted of base 
metal aluminum, coated thinly on one side with an 
alloy of low melting point. The unit was assembled 
in a brazing furnace where all joints were formed si- 
multaneously with the aid of proper fluxing. The two 
stampings assembled in one operation the final unit 
case, a ball, bearing the filler bushing and fuze ring. 
No difficulty was encountered in producing uniform 
and tight joints, except in the sealing plug, which 
screwed into the female bushing. Here there was 
some indication that in the brazing process the 
threads of this bushing were distorted and no longer 
met the original rigid specifications. It seems likely 
that, if large-scale production should be undertaken, 
it would be advisable to cut these threads after the 
brazing operation. 

Filling of the unit (see Section 4.4) was accom- 
plished through the %-in. bushing and, in the case of 
WP > by the use of an automatic dry-loading machine 
operated at Edgewood Arsenal. Closure was accom- 
plished by an air torque wrench exerting 200 in-lb 
pressure on a J^-in. long plug. With the high torque 
quoted, it was found necessary to use a thicker female 
bushing than originally designed. 

The compatibility of aluminum and various alloys 
was demonstrated by data supplied by Edgewood 



THE FUZE T-21 


25 


Table 1 . Weight and filling relationships for various WP Beano cases. 



A 

B 

C 

D 

E 

F 

G 

H 

Weight, ounces 









Case 

4.52 

2.38 

4.960 

5.45 

1.586 

1.37 


1.191 

Cup 

0.488 

0.488 

0.626 

0.608 

0.193 

0.193 


0.154 

Ring 

0.112 

0.112 

0.208 

0.208 

0.208 

0.208 


0.112 

Top 







1.171 


Bottom 







0.490 


Plug 







0.015 


Total 

5.120 

2.980 

5.794 

6.266 

1.987 

1.771 

1.676 

1.457 

Fuze 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

Complete unit (less filling) 

Wt of filling which will give a total unit wt 

7.62 

5.48 

8.29 

8.76 

4.48 

4.271 

4.17 

3.96 

of 12 oz 

4.38 

6.52 

3.71 

3.24 

7.52 

7.73 

7.83 

8.04 

WT of WP if 10% void allowed 

Per cent of total possible with total unit wt of 

8.0 

8.0 

8.0 

8.0 

8.0 


8.0 

8.0 

12 oz 

54.8 

81.4 

46.3 

40.5 

94.0 


97.8 

100.0 


A Standard HE Beano case made from 0.040 steel with short-style* steel cup and brass hold-down ring. Filling vol 140 cc. 

B HE Beano style case made from 0.020 steel with short-style steel cup and brass hold-down ring. Filling vol 140 cc. 

C HE Beano style case made from 0.040 brass with short-style brass cup and brass hold-down ring. Filling vol 140 cc. 

D HE Beano style case made from 0.040 copper with short-style copper cup and brass hold-down ring. Filling vol 140 cc. 

E HE Beano style case made from 0.036 2S aluminum with short-style aluminum cup and brass hold-down ring. Filling 
vol 140 cc. 

F HE Beano style case made from 0.032 No. 21 brazing sheet with short-style aluminum cup and brass hold-down ring. 

This unit was made 3" OD rather than the 2J^" used on the other metal units. Over size. 

G Northern Industrial Chemical Co. Ethocel unit. Outside diameter 2fU (Figure 2). 

H HE Beano style Plax Corporation Ethocel unit with short-style Ethocel cup and brass hold-down ring. Filling vol 140 cc. 


* Short-stvle cup. In the WP Beano, because of the reduced tetryl charge, it has been possible to reduce the length of the 
former cup by J4 inch as compared to the cup used in the HE Beano unit. 


Arsenal 8 where it was reported that on continuous 
immersion at atmospheric temperature, aluminum in 
WP showed no penetration greater than 0.008 in. per 
100 months and this occurred almost entirely within 
the first 168 hours. The same conclusion was drawn 
by independent testers who employed temperatures 
up to 100 C with both dry and wet WP. 13 Under the 
same conditions, steel was considerably more sus- 
ceptible to attack. 

Table 2 summarizes the characteristics of the pro- 
duction model (Figure 2). 


4,3 THE FUZE T 21 

The only changes in the T-5 fuze necessitated by 
the new case and filling of WP Beano were in the size 
of the bursting charge of tetryl, the small aluminum 
cup which held the burster, and the length of the 
former cup which accommodated the fuze. With the 
case described above, data such as that given in 
Table 3 indicated that the burster charge of tetryl 
could be reduced to nearly one-half that used in the 
high explosive Beano while providing the apparent 
optimum compromise between WP fragmentation 


and the area of particle distribution. In the final fuze, 
the burster charge was set at 1.30 g. With the re- 
sultant saving in space, it was possible to reduce the 
length of the former cup volume required by the T-5 
fuze and thus to increase further the payload of the 
grenade. 

Table 2. Characteristics of production Model WP 
Beano case. 

No. 21 aluminum brazing sheet 
XJ51S aluminum alloy 

Material of construction for machine parts 


Wall thickness of case, inch 

0.032 

Weight in ounces: 

Fuze less tetryl 

2.62 

Empty case 

1.94 

Tetryl 

0.05 

Total empty unit 

4.61 

Allowable for filled unit 

12.00 

Allowable for WP 

7.39 

WP to be put in unit 

7.22 

Volumes in cubic centimeters: 

7.22 oz of WP 

117.5 

Total available for filling 

131.0 

Voids 

13.5 

Void volume as % of total volume 

10.5 

Efficiency of loading 

97.8% 


26 


WP BEANO (OD-176) 


Table 3. Number of hits of WP y and in. on 90- 
degree vertical target.* 


Tetryl 

charge 

5 yd 

10 yd 

15 yd 

20 yd 

0.75 

36 

45 

12 

9 

1.00 

625 

35 

7 

2 

1.25 

797 

31 

5 

4 

1.50 

443 

88 



2.00 

189 

29 

0 

3 


* (Orientation: Fuze up) 


4 4 THE FILLING 

4.4.1 Alternatives 

In addition to WP itself, fillings of a modified na- 
ture were considered. Chief among these were PWP 
(WP plasticized with a gel of xylene and GRS 
rubber 4 ’ 7 > 10 ) and SWP (WP reinforced with steel 
wool). 11 Other attempts to alter the filling by the ad- 
dition of rock wool, glass wool, cotton, and so forth, 
were given only cursory trials. 

In brief, the dispersion and antipersonnel behavior 
of PWP and SWP were consistent but different from 
WP. The tendency in both PWP and SWP was to 
produce fewer and larger particles of the burning 
filling and to throw these a greater distance. Typical 
data giving the optimum performance of all three 
fillings are presented in Table 4. It should be noted 


Table 4. Number of hits of WP and y 2 in. on 
vertical 90-degree targets. 


Filling 

Tetryl 

charge 

5 yd 

10 yd 

15 yd 

20 yd 

WP 

1.25 

797 

31 

5 

4 

PWP 

1.50 

80 

7 

0 

3 

SWP 

2.00 

463 

17 

9 

8 


that the different fillings require different burster 
charges for optimum performance. 

In view of the original requirements for maximum 
effect in the area closest to the point of burst, neither 
PWP nor SWP was given further attention. The 
work was abandoned, with the approval of the vari- 
ous Services, because only WP was, at the time, a 
standardized filling, and because there was no defi- 
nite proof that PWP and SWP were equal to WP in 
antipersonnel behavior on a volume basis. 

4.4.2 WP Filling 

The decision as to whether WP should be loaded in 
this munition dry or wet was made by the Chemical 
Warfare Service. In the experimental loadings made 


at Edgewood Arsenal, an automatic dry-loading tech- 
nique gave most satisfactory results. The inverted 
body received a delivery vacuum tube through the 
bushing hole, and loading was made to the lower edge 
of the bushing. The resulting void of about 10 per 
cent in the filled grenade 6 was a desirable feature, in 
view of the extreme expansion coefficient of WP. 
Closure was made, as already described in Sec- 
tion 4.2.2, with the assistance of a standard luting 
compound (Federal Specification II-W-261a), con- 
sisting of a mixture of 16 per cent linseed oil and 
84 per cent basic lead sulfate. These procedures 
coupled with the use of a pipe plug, meeting the 
Army-Navy Aeronautical Specification AN-GGG- 
P-363, gave lots with less than 1 per cent leakage, 
thus comparing favorably with the results from 
standard munitions. Because of low surface tension, 
WP has always been a difficult material to seal. 

4.5 SURVEILLANCE 5 

The seals for the production units were tested 
primarily in two ways, first, by static storage at —30 
to 150 F with the plug closure down, and, secondly, 
by the Army Ordnance Jolt and Jumble Test. The 
former was by far the more severe and was ulti- 
mately met by the use of the methods given in Sec- 
tion 4.4.2. 

4.6 PERFORMANCE 1 

Qualitative evaluation of the burst was possible 
with visual observation but a more accurate ap- 
praisal was obtained by using semi-circular targets 
grouped in 90-degree arcs around a center point at 
which the grenade was detonated. These targets con- 
sisted of individual manikins mounted upright. The 
number of splashes of WP greater than or 3^ in. 
was counted after each shot. An accurate estimate of 
effectiveness required counting the number of similar 
hits on the enclosed area, hence a wooden floor was 
provided within the 10-yd circumference. Because of 
the slow velocity of WP gobs, those which fly up- 
ward and fall in lobs of high arcs may still be classi- 
fied as effective, in contrast to similar particles of a 
high explosive grenade which would be valueless. So 
that there might be no ambiguity in these tests, the 
grenades were detonated by the impact of the T-21 
fuzes when they fell from a specially designed drop- 
ping-tripod, which was operated by remote control. 

Representative data of the burst pattern of the 
production model showed that, for most orientations 




PERFORMANCE 


27 


of the grenade, the coverage at 5 or 10 yd was uni- 
form. Only when the filler bushing was pointing at 
the target was the coverage seriously less. This is 
perhaps accounted for by the behavior of the filler 
bushing and plug which were expelled as a unit on 
detonation. Also, a large amount of the WP filling 
tended to be thrown through the fuze opening. In 
terms of hits per unit area, the average for a 5-yd arc 
was 6.5 hits per sq ft, while for a 10-yd arc the aver- 
age was 0.42 hits per sq ft. It is thus seen that the 
density for a vertical target at 5 yd was over 15 times 
that at 10 yd and that the frontal area of a man 
would receive 47 hits at 5 yd and 3 at 10 yd. These 
figures may be compared with 3.5 and 0.24 hits to be 
expected from the Mark 15 standard WP smoke 
grenade, and 1.2 and 0.01 hits from the British 
No. 77 grenade. This comparison is even more favor- 
able when the three are adjusted by calculation to 
the same weight basis (see Table 5). The purpose of 


Table 5. Average hits per sq ft of vertical target 
area per 7 oz of WP. 


Grenade 

5 yd 

10 yd 

WP Beano 

6.5 

0.42 

CWSM15 

1.75 

0.12 

British No. 77 

1.05 

0.01 


these last two grenades, it should be noted, was 
primarily to make smoke. 


A study of the area patterns indicated a tendency 
to a high density of hits in the direction in which the 
fuze was pointing and a rapid drop in density beyond 
6 ft from the point of burst. The material which was 
lobbed into the air seemed to produce a band of in- 
creased density 15 ft from the burst. 

These facts when coupled with ease of aiming and 
throwing, made this seem an effective weapon for 
limited use wherever an attack with fragmentation 
grenades could be improved by an interspersal of 
WP. The user had little to fear from the burst, be- 
cause the fragmentation of the thin aluminum case 
produced only large fragments, which quickly lost 
their velocity. Only the filler bushing and the brass 
parts of the fuze could travel distances of as much 
as 60 yd. 

The decision to accept WP splashes of 34 to Yi in. 
or larger as casualty producing was based on many 
reports issued by both the British and American 
Armies. The amount of WP sought was, therefore, a 
minimum of about 150 mg, 14 a quantity which would 
burn through at least two layers of battle dress. 
Smaller particles would be considered chiefly har- 
assing, unless they happened to hit some unpro- 
tected part of the body. Naturally, several simul- 
taneous hits would be more than correspondingly 
effective, thus giving point to the discussion of den- 
sity of hits. 4 



Chapter 5 


SPIGOT MORTAR 


5.1 INTRODUCTION 1 

The weapon described in this chapter is, in the 
writer’s opinion, quite novel, although the principle 
of the spigot has been applied before and weapons 
based on it are well known. The Spigot Mortar was 
originated by a group in Britain known as the Inter- 
Services Research Bureau, who had carried it into 
full production in Britain but on a scale too small to 
supply American, as well as British, requirements. 
At the request of OSS, and with the full support and 
cooperation of the British, 2 Division 19 assumed the 
task of supplying to interested Services sufficient 
American samples for an appraisal of the place of the 
Spigot Mortar in American operations. The groups 
thus acquainted with the device included the Army 
Ground Forces, the Army Ordnance, the Bureau of 
Ordnance, and the Marine Corps. Samples were 
eventually despatched to the Infantry Board at Fort 
Benning, Georgia, 8 and to the Aberdeen Proving 
Ground, Aberdeen, Maryland, but the reports of 
these groups were not available at the time of writing 
this chapter. 

The Spigot Mortar was a weapon capable of throw- 
ing accurately a projectile, carrying 3.1 lb of high 
explosive and an impact fuze, over a distance of 
200 yd or less without appreciable noise or flash. 
These last two features were the ones which made the 
device unique and recommended its consideration in 
a number of special operations, which might logically 
include attack on fixed installations, either by time 
delay or manual operation, or on moving targets by 
booby traps. Because of the noiseless and flashless 
features and the element of surprise, the danger of 
discovery could be considered negligible. 

The total weight of the gun, sight, and one bomb 
did not exceed 12 lb, making it easy for an individual 
soldier to operate effectively against specially se- 
lected targets, and to carry, if desired, more than one 
round. In some ways, the Spigot Mortar can be con- 
sidered a useful complement to the rocket launcher 
described in Section 1.3. It definitely should not be 
considered a competitor, because its range is much 
shorter and the rocket is extremely noisy. 

As ordinarily used, the mortar required a tree or 
other support, such as a masonry wall or a pole, for 
attaching the gun and absorbing the not inconsider- 


able recoil. This limitation on its usefulness was not 
considered serious and was partially rectified by the 
development of a plate support allowing the firing of 
the gun at all locations on solid ground. 

The Spigot Mortar was in production by OSS at 
the end of the war. So far as is known, it did not 
reach the field for combat use. 

5.2 THE gun 14 

The gun consisted essentially of a base and a % in. 
spigot and weighed in all 4^ lb. The base was pro- 
vided with a screw so that it might be screwed by 
hand into a support, which was generally a tree of 
over 6-in. diameter. As an aid in removing bark and 
obtaining a smooth bearing surface for the base, one 
of the two 43^-in. lever arms had a chisel ending. 
The other arm was provided with a hole through 
which a trip wire could be guided when booby trap 
firing was preferred. 

The spigot was attached and mounted at the base 
by a ball and socket joint composed of the spherical 
head of the screw and a cover plate held to the base 
by three screws, two of which were simple cap screws 
ordinarily remaining fixed at a preselected adjust- 
ment. The third screw was provided with a movable 
T-handle which, when loose, allowed free movement 
of the spigot in the ball and socket joint, but, when 
tightened by a turn of the wrist, locked the spigot in 
the desired location. 

The spigot was hollow and housed a spring-actu- 
ated striker which was cocked by a simple pull on a 
lanyard and held in cocked position by a trigger. 
The spigot tube was mounted firmly in the base and 
delivered to it the thrust produced by firing the 
round. This was accomplished by the release of the 
trigger, which allowed the compressed spring to pro- 
pel the firing pin forward. The small pointed end of 
the firing pin projected through a small hole in the 
forward end of the spigot tube and struck the sensi- 
tive primer cap of the propellent cartridge in the 
bomb tail. 

The maximum elevation allowed when using a 
vertical support for the gun was about 23 degrees, 
giving an effective range of slightly over 200 yd. An 
assembled gun and the various parts referred to 
above are shown in Figure 1. 




mmmmm 


& 


28 


THE LIVE BOMB 


29 



Figure 1 . Spigot and component parts. 


No new principles were involved in the construc- 
tion of the sheet steel (No. 14 gauge) plate-mounting 
which allowed the use of the gun where no support 
other than firm ground was available. The gun was 
mounted in a plate by means of a trunnion and two 
bearings, allowing a greatly increased traverse for 
aiming in the vertical plane. The plate was so con- 
structed that the two circular rings would cut into 
the earth when the plate was seated by rotation and 
oscillation. One trial shot was generally sufficient to 
embed the plate solidly in the ground, where it could 
then be more firmly held by driving in spikes. Re- 
moval required very little effort. 

5.3 THE SIGHT 16 

The sight, as shown in Figure 4, slid over the spigot 
tube and was fixed in position during aiming by a 
locking screw. After the gun was positioned and se- 
cured, the sight was removed and replaced by the 
bomb. Figure 2 shows this sight, in two views 
mounted on a spigot tube as though in use, and in 
the third folded for carrying. Folded, it measured 
1 1 3^6 i n - thick, 3% in. wide, 5 % in. long, and it 


weighed about 1.2 lb. This sight was entirely an 
American development and was a simplification of 
the British design. 6 The one shown was for the tree- 
mounted gun. A modification for high angle trajec- 
tory fire would be needed for the plate-mounted gun. 

Ordinary use of the sight required its positioning 
as seen in the upper left view of Figure 2. The user 
standing back to the target and bent over saw an 
erect image while both his hands were free to adjust 
the gun. The sight was a one-power, right-angle tele- 
scope calibrated in 25-yd increments by the use of 
the peep-hole bored sight shown in the lower right 
corner of Figure 2. In those cases when the operator 
wished to sight from cover, such as tall grass, a 
trench, or foxhole, the eyepiece was turned down- 
ward, as shown in the lower left view. However, the 
body of the sight was always mounted vertically 
above the spigot tube. In all cases crosshairs marked 
the target. 

5.4 THE LIVE BOMB 

Figure 3 shows the assembled bomb and the vari- 
ous component parts, exclusive of the propellent 


/’RESTRICTED 1 


30 


SPIGOT MORTAR 



Figure 2. 

cartridge. The bomb consisted of a tubular tail carry- 
ing a propellent cartridge, a silencing wad made of 
soft brass, a screw-cap end-piece and a dust plug, an 
impact fuze and its housing, and a soft steel head 
with cap opening for filling with high explosive. The 
head was attached to the tail by locking the hooks on 
the underside of the head into a plate located in the 
cone of the tail. 

5.4.1 The Tail 

The most difficult part of the whole weapon to 
provide was the tail tubing, for this had to withstand 
the tremendous pressures developed by gases from 
the burning propellent cartridge, and to seal them 
completely from the air. It was this which made the 
weapon flashless and noiseless, the unique features 
which gave it its chief value. The tube shown was 
found by actual tests to withstand pressures below 
49,000 psi, a safety factor of 2.5, which allowed the 
possible increase of the propellent charge by perhaps 
60 per cent, with probably attendant increase in 
range to 275 yd. 7 No development along these lines 
was completed because of time limitations, but future 
work of this kind would seem profitable, and it would 
doubtless entail a strengthening of the gun mount. 

The tail tubing was built up of three seamless steel 


Sight, 

tubes of SAE 3140 specification sweated together and 
sealed with a thick steel plug silver-soldered in place. 

5.4.2 The Cartridge 

This was a specially constructed 12-gauge car- 
tridge (FLI-S18), consisting of a cylindrical paper 
tube, a copper cap (outer base), and an aluminum 
and composition disk (inner base) bearing in its cen- 
ter a detonator. The filling was a special nitrocellu- 
lose mixture developed for the purpose by the Federal 
Laboratories of Pittsburgh, Pennsylvania, and its 
waterproofness was assured by a double coating of 
Sargent Paraffin Hard. 11 

The cartridge, assembled in the bomb tail and 
backed by a soft brass wad bearing a small hole to 
allow penetration of the firing pin contained in the 
spigot, was fired by the blow, with a resultant ac- 
celeration of between 1,800 and 2,200 g on the bomb, 
thus imparting an initial velocity of about 200 ft per 
sec. The pressure generated by the burning of the 
cartridge forced its copper base cap and the adjacent 
wad down the tail tube, where they came to rest 
against the screwed-in stop ring in the base of the 
tail. An essentially gas-tight seal resulted and the 
necessity for overlapping tail-tube construction is 
now explained. 


OPERATION AND PERFORMANCE 


31 



Figure 3. Bomb and component parts. 


5.4.3 The Fuze 

Delays in delivery and certain inconsistent per- 
formance by the British fuzes 3 prompted a study of 
this part and the development of an American fuze 
based on the T-5 (see Section 3.4). This American 
fuze was armed by the release of an inertia pin oper- 
ating under application of about 122 g, a force well 
beyond anything likely to be encountered acciden- 
tally, and yet sufficiently below that given by the car- 
tridge to assure certain functioning. To prevent firing 
from rearward movement (which might occur when 
the wad and cartridge base met the stop ring), the 
“all ways” features of the T-5 fuze were sacrificed, 
with the result that firing was not always obtained 
on glancing impacts of low angle. 8 Calculations indi- 
cated that the fuze became armed before the bomb had 
entirely left the gun, a feature which could perhaps be 
corrected by an alternate design which would provide 
arming after an elapsed time of 1 or 2 sec. Such a fuze 
did not exist in Ordnance procurement at the time of 
this development and would have great advantages 
in many munitions, if it could be developed. A very 
preliminarjr attempt was made to solve the problem. 12 

5.4.4 The Head 

Two bomb heads were constructed, one to use with 
a poured charge and one to use with a molded charge, 


the latter type being preferred by the Americans 
while the former type was standard with the British. 
Both were made of light steel stampings and con- 
tained a soft brass insert to house the fuze. In prac- 
tice, it was found that the light steel cover made very 
close contact with the target before the fuze had 
time to operate and thus insured optimum perform- 
ance of the high explosive. A filler plug sealed the 
head after it was filled. 

It was shown that filling of the heads could be done 
practically, either prior to delivery using cast pento- 
lite 10 or in the field with plastic explosive (Compo- 
sition C-2). 9 

5.5 OPERATION AND PERFORMANCE 

The user, having screwed the gun into a suitable 
large tree, having aimed the spigot with the sight, 
and having replaced the sight with a loaded bomb, 
had the choice of three firing methods : the first was 
by manual operation of the trigger release cord; the 
second was by use of a time delay Pencil (see Chap- 
ter 9), from which the spring snout had been removed 
to allow free passage of the delay plunger against the 
trigger of the gun; the third was by the connection to 
the trigger release of a trip wire, as in standard 
booby-trap practice. 

The muzzle velocity was determined by firing 
through Boulange screens 18 ft apart. Its mean value 


32 


SPIGOT MORTAR 



Figure 4. Spigot with sight. 

was 195.6 ft per sec with a mean deviation of 0.69 per 
cent, which corresponds to a deviation in range of 
1.4 per cent. The mean deviations observed with in- 
ert filled bombs were 7.4 per cent at 50 yd, 1.5 per 
cent at 100 yd, and 1.3 per cent at 150 yd. This indi- 
cated that at these ranges the deviation was caused 
by varying muzzle velocity and was attributed to 
variation in the performance of the propellent car- 
tridges. Wind direction had some effect, as could be 
predicted, for such a large and relatively slow pro- 
jectile, but could be compensated for by an expe- 
rienced operator. Disregarding this, a 100-yd range 
gave deviations in elevation and line of approxi- 
mately ± 2 ft and ± 1 ft, and was regarded as the 
maximum effective range for targets as small as 
tanks or automobiles. 4 


Figure 5. Spigot with bomb. 

Tests with trained personnel indicated that the 
Spigot Mortar could be removed from a carrying 
rucksack, mounted, aimed, and fired within 2 to 

4 minutes. 

The effectiveness of the charge against various 
targets can be judged from the following: (1) on 2- to 
2J^-m. armor plate, blisters with a 14 in. diameter 
were projected from the back of the plate and a hole 

5 in. in diameter was made through the plate; (2) on 
reinforced concrete 9 in. thick, an opening of 18 to 
24 in. resulted; (3) an automobile was completely 
demolished; and (4) a locomotive was so damaged 
that it required a month’s repair. 5 

It is believed that a most effective and novel 
weapon was developed and that, in special opera- 
tions, it could harass the enemy seriously. 


Chapter 6 

SLOW BURNING EXPLOSIVES (SBX) 


6.1 INTRODUCTION 

The work of Division 19 on SBX originated in a 
search for unconventional and yet readily available 
materials which would be capable of inflicting severe 
damage to enclosed structures, such as storage ware- 
houses and ship’s holds. The hazards common to in- 
dustries handling finely divided carbonaceous ma- 
terials immediately suggested that dust explosions, 
properly controlled and produced, might be a valu- 
able military technique. This thought was not origi- 
nal with the division, since a large amount of work 
had already been done in England, chiefly on coal 
dust, 20 with, from the theoretical point of view, 
slightly disappointing results. 

In this country, a study of many years duration 
had been underway at the Bureau of Mines and this 
also centered primarily on coal dust, although many 
other materials, including fine organic and metallic 
dusts, had been investigated to a more limited ex- 
tent. 2 It was thus well known 1 that practically all 
finely divided combustible materials, if properly dis- 
persed and mixed with air in correct proportions, 
would burn, when ignited, with a violence and speed 
of possibly explosive proportions. 

The difference between inflammability and explo- 
sibility, being one of degree rather than kind, the fol- 
lowing experimental quantities were indices of the 
course to be followed: (1) relative inflammability 
should be high for a military explosive, (2) limit of 
explosibility should be low, (3) the pressure de- 
veloped would depend on both the heat of com- 
bustion and the ventage of the chamber where the 
explosion would take place, and (4) the rate of pres- 
sure increase would be a measure of the speed of com- 
bustion. The last point indicates the chief difference 
between high explosives and SBX, SBX being of 
military value only in those cases where the maxi- 
mum pressure effect over a relatively long time is 
important, or where ventage is small and confine- 
ment good. In so far as heat of combustion is con- 
cerned, high explosives are in no way comparable to 
combustible dusts, as indicated in kg-cal per g for 
the following materials: black powder, 0.7; dynamite 
(75 per cent), 1.3; TNT, 3.6; coal, 7.6; pitch, 8.4; 
aluminum, 14.1; magnesium, 6.0; and sulfur, 2.2. 

With this background of work in mind, the central 
laboratory of the division conducted experiments on 


the development of a dust disperser and igniter, and 
studied a number of materials which in dispersed 
form might give suitable performance in confined 
space. The work was done with no thought of more 
orthodox military applications and it does not appear 
that SBX can seriously compete with high explosives 
for use in bombs or shells. The effectiveness of SBX is 
limited to confined structures where the ventage is 
small, and by hazards in its loading, and the number 
of likely targets. However, where a special target has 
been selected for attack or demolition by a small 
group of specialists, SBX would appear superior to 
high explosives, both because of its availability in the 
field and because its slow pressure increase in a con- 
fined space might eventually cause greater damage 
through structural failure than would a comparable 
amount of fast acting high explosive whose effect 
would be to punch or cut rather than demolish. 7 

This new work of Division 19 with the cooperation 
of Division 2 and Division 11 personnel resulted in 
two major developments: the new SBX material 
called Salex 10 - ll - 12 (a compressed mixture of sulfur 
and aluminum), and Lulu, 1 ’ 5 a disperser-igniter for 
use with all SBX materials. In the course of the work, 
many different substances were tested using a num- 
ber of measuring gauges, two special explosion-proof 
rooms, wooden buildings, and a ship. From this work 
it was concluded that Salex was not as effective, on 
either a weight or volume basis, as a number of other 
SBX substances, chief of which were aluminum and 
gasoline when dispersed and ignited by Lulu. This 
igniter, being small and simple to construct, was be- 
lieved valuable for certain uses of a clandestine na- 
ture. If necessary, it could even be dispensed with by 
the use in the field of suitably cased Torpex or TNT 
blocks. In brief, a method for attack on closed struc- 
tures was discovered and the tools best suited for the 
purpose were made available. 

6.2 SBX MATERIALS 414 

There is no scarcity of common materials which 
can be used for this purpose. An early British memo- 
randum lists, for example, 35 different substances 
likely to occur in manufacturing plants, to disperse 
easily, and then to ignite explosively with a small 
heat source such as a lighted match. In addition, it 


33 


34 


SLOW BURNING EXPLOSIVES (SBX) 


lists 19 more, which will behave similarly when ex- 
posed to higher heat. 4 Almost all of these SBX ma- 
terials were organic and carbonaceous, and, of them 
all, flour seemed most available and worth trial. 
Early trials with 5-lb sacks indicated that dispersal 
was best obtained using 75 or 100-g charges of TNT, 
and that black powder and blasting powder were not 
uniform or complete in action. As was to be expected 
from the Bureau of Mines work, 2 no ignition of dis- 
persed flour dust was obtained by using TNT alone. 
It was obtained, however, when the high explosive 
was surrounded by coarse magnesium flakes, 3 and 
this was the origin of Lulu (Section 6.3). 

Other carbohydrate dusts, including graham flour, 
starch, and sugar, gave results comparable with 
those of white flour. In general their efficiency was 
low (about 20 per cent), when compared, by assum- 
ing values of peak pressure, or impulse, and time of 
burning, with calculations made from a simplified 
theory of SBX. 15 By assuming that SBX pressure 
arises solely from temperature increase, that all the 
heat of combustion is used in this way, that burning 
is at a uniform rate, and that the ratio of maximum 
SBX pressure to atmospheric pressure is small, ex- 
pressions dependent on the volume of confined space, 
the ventage, the chemical nature of the SBX mate- 
rial, the heat of combustion, and the charge size were 
derived. Efficiency is the value thus calculated, com- 
pared to that actually obtained from measurements 
of the total impulse and pressure-time curves. 

Low efficiency may be accounted for by energy 
losses: first, because part of the charge may have 
escaped complete combustion through loss in ventage 
or unfavorable combustion conditions, secondly, be- 
cause of variation in the ease with which a given 
SBX material can be completely burned, and thirdly, 
because of the large loss of radiant heat to the cold 
walls of the test structure. In all SBX materials, 
these three important points are difficult to evaluate, 
the second one Pnly being a function of the chemical 
nature of the combustible substance. In the case of 
carbohydrates, such as flour, the second factor is ap- 
parently very large. At any rate these materials are 
poor for SBX purposes. 

The efficiency of both coal and hydrocarbon dusts 
was nearly 20 per cent, while that of metal dusts 
(aluminum and magnesium) was about 35 per cent, 
flaked aluminum being superior on a weight basis 
and atomized aluminum being preferable on a vol- 
ume basis. These were definitely inferior to liquid 
SBX materials, such as benzene and gasoline, the 


efficiency of which was 35 to 40 per cent, and carbon 
disulfide, the efficiency of which reached 70 per cent. 
However, in the case of these liquids, there was a 
long induction period (at least when Lulu was the 
disperser-igniter) which, with moderate ventage, re- 
sulted in loss of pressure. 

A combination of aluminum dust and liquid SBX 
materials was shown to eliminate this trouble en- 
tirely and, at the same time, to increase the apparent 
density. For example, 10 lb of aluminum and gasoline 
mixture (d 1.25) per 8,000 cu ft volume gives an SBX 
pressure of 15 to 20 psi (1-3 lb was considered suffi- 
cient to demolish an ordinary masonry or wooden 
structure). 

An attempt to produce a mixture of sulfur and 
aluminum which would supposedly show the theo- 
retical maximum effect was not entirely successful. 
The optimum combination of Salex, in either a cased 
or uncased unit, contained 75 to 85 per cent alumi- 
num compressed with sulfur to 3,000 psi and a dis- 
perser-igniter of tetryl representing 10 to 25 per cent 
of the total unit by weight. For such a munition, the 
calculated total heat of combustion was two-thirds 
more than that for a similar weight of TNT, but this 
energy could not be freed completely. 17 Many vari- 
ations in the relative proportions of the two ingredi- 
ents, in the burster charge, in the type of case, and in 
the addition of carbon disulfide, failed to improve 
efficiency, which was always below TNT when used 
without additional SBX material, and always below 
Lulu when used with SBX material. Only tactically, 
in that it formed a non-persistent poison gas, did 
Salex have any attraction over other SBX ma- 
terials. 10 

Typical time-pressure curves for the various SBX 
substances tested, and, in some instances, the calcu- 
lated performance curves are given in Figure 1. The 
value for Salex would be between the values for 
tetryl and flaked aluminum. 

6.3 DISPERSER-IGNITER (LULU) 69 

Having discovered that high explosive was, by a 
large factor, superior as a disperser to black powder 
or blasting caps, and having ascertained that a sur- 
round of magnesium chips was needed to insure ig- 
nition of the dispersed dust-air mixture, a more exact 
definition of the high explosive, the amount and spec- 
ification of the surround, the type of casing for the 
complete unit, and the size of the Lulu best suited for 
convenient amounts of SBX material, was needed. It 


PRESSURE- PSI 


DISPERSER-IGNITER (LULU) 


35 



TIME-MILLISEC 


Figure 1 . Comparison of results of theoretical calcu- 
lations of SBX pressure-time characteristics with 
actual studies. 



Figure 2. Effect of mixing aluminum with gasoline 
using Lulu burster, large venting and space gauge. 


was soon apparent that magnesium flakes, while de- 
sirable and in no case harmful, were unnecessary in 
the better SBX substances, such as gasoline, but 
were essential for the poorer ones, such as flour. In 
the final model, therefore, magnesium in sufficient 
amount to insure good performance with flour was 
specified. 

It was found also that the case could be, equally 
well, cardboard, steel, or aluminum, so far as dis- 
persing and igniting were concerned. In the final 
model, aluminum was chosen for its lightness and 
availability and its tightness against the liquids, pre- 
ferred as SBX charges. (It will be remembered that 
some high explosives are soluble in gasoline or ben- 
zene.) Without loss of performance, the choice of 
high explosive might well have been TNT, tetryl, or 
Torpex, for all three produced identical results, but, 
because of cheapness and availability, TNT was 
specified. 

The final Lulu disperser-igniter consisted of 360 ± 
5 g of a 60-30-10 mixture of granular TNT, mag- 
nesium Grade C, and magnesium Grade B loosely 
packed into an aluminum casing (Alcoa 24 ST 16 
gauge, round tubing 2 in. OD and 12 in. long) carry- 
ing screw caps (24 threads per in.) at both ends. 
Holes were there provided for shipping plugs which 
could be removed and replaced by the initiating sys- 
tem consisting of a booster assembly (TIE2 or British 
Type 6) and a delay mechanism such as a clockwork 
or a-c delay (see Chapters 12 and 13) or a standard 
engineer pull switch for lanyard operation or booby 
trapping. 

This standard Lulu was too large for convenient 
testing and most of the results recorded here were 
obtained with scaled down charges and the so-called 



36 


SLOW BURNING EXPLOSIVES (SBX) 


A B 



Figure 3. Comparison of disperser-igniters. A. Effect of nature of burster with flour. B. Effect of nature of burster 
with gasoline. 


Baby Lulu, a similar unit containing only 135 g of 
the TNT mixture. The standard unit was adequate 
for dispersing and detonating about 100 lb of flour 
and similar dusts, or several gallons of liquid. Since 
these materials were readily obtainable in military 
dumps, the Lulu weighing only 2 lb could be recom- 
mended for field use by an individual soldier. With- 
out burdening, it gave him a powerful weapon for 
special use. 

This, of course, could not apply to Salex, which 
was in the nature of an SBX material itself and was 
very inefficient for dispersal and ignition of other 
materials. 

6.4 VENTING 

Of paramount interest in SBX discussion, is the 
amount of venting or the ratio of vent area to en- 
closed volume. The general effects for extreme cases 
are easily foreseen. In the open, an SBX bomb would 
spend itself harmlessly and, because of its low speed 
of detonation, could not be counted on to throw frag- 
ments of casing or shrapnel forcefully over a distance 
comparable with that for high explosives. In the 
other extreme case, where no venting is available, 
the pressure on the walls of the confining structure 
would become enormous and, when the limit of their 
elasticity had been passed, would collapse with com- 
plete demolition of the structure. This would be a 
most favorable case for SBX, and one in which high 
explosives would not perform so well, because of 
their low heats of combustion and the shattering 
speed with which they detonate. 

A choice of the correct amount of SBX material 
for a given volume depended, therefore, on the vent- 


age for that volume and the other factors inherent 
in SBX which have been mentioned in Section 6.2. 
Figure 4 shows the effects of varied charge sizes for 
constant venting, while Figure 5 shows the effect of 
changed venting for constant charge. 

The curves are based on data obtained from the 
use of a specially constructed underground test- 
house, a concrete structure measuring 30 ft in length, 
and having a total capacity of approximately 
4,320 cu ft. The open end and a part of the adjacent 
roof were provided with movable shutters and plank- 
ing so that the opening could be controlled at will. 
The three openings most commonly used were 10, 20, 
and 40 sq ft, and designated small (S), medium (M), 
and large (L), respectively. For the more inefficient 
SBX materials, the M opening was used ; for gasoline 
and aluminum and mixtures of them, the L opening 
was necessary to protect the structure from damage. 16 
The position of the charge within the structure was 
irrelevant, because the pressure obeyed hydrostatic 
laws. 

A quantitative recommendation to the field was 
difficult but was about 0.05 oz per cu ft. 5 In a struc- 
ture or space with approximately M ventage, the 
action of a 100-lb bag of flour on a volume of about 
10,000 cu ft insures demolition. The same result would 
also be obtained with a gallon (about 30 lb) of gaso- 
line or a sludge of aluminum powder and gasoline, 
and such materials would be expected to build up 
slowly (in 10 to 15 milliseconds) to a maximum pres- 
sure of several pounds per square inch and to main- 
tain that pressure for a period of perhaps 50 milli- 
seconds, a time which would certainly be sufficient to 
demolish all but the strongest construction. Even a 




INSTRUMENTS FOR EVALUATION OF SBX 


37 


A B 



Figure 4. Comparison of charge size and venting. A. Effect of charge size with flour. B. Effect of charge size with 
gasoline. 


A 


B 



Figure 5. Comparison of charge size and venting. A. 
materials. 



TIME - MILLISEC 


Effect of venting with flour. B. Effect of venting with various 


structure with a number of glass windows could be 
considered closed, for while the glass would break 
easily under a sudden blow (such as from a high ex- 
plosive) it would withstand for a considerable time 
the slow increase in pressure provided by SBX, and, 
in the end, the masonry could be expected to yield 
first. 12 

6.5 INSTRUMENTS FOR EVALUATION 

OF SBX 8 - 13 - 16 

An accurate measurement of the peak pressures, 
as well as the intermediate pressures, at various 
times was essential for an appraisal of SBX sub- 
stances. This was accomplished by using a number of 
different gauges which gave fairly consistent results, 


so that there was reason to believe that the quanti- 
tative comparisons inferred had a firm basis in fact. 15 

For the study of the characteristics of underwater 
explosive waves, Division 2 had developed tour- 
maline piezoelectric gauges which, through the co- 
operation of this division, were found satisfactory 
for SBX study and superior to similar Rochelle salt 
gauges, commercially available. After thermal in- 
sulation to prevent spurious pyroelectric signals, 
these gauges gave most satisfactory performance. 

A second type gauge, based on a condenser of Gen- 
eral Motors design 21 gave continuous time pressure 
curves comparable to the tourmaline gauges. 

A third type developed by the Factory Mutual 
Research Corporation 13 was based on a mechanical 
principle and consisted essentially of a piston, the 


38 


SLOW BURNING EXPLOSIVES (SBX) 


mass of which per unit area was equal to that of the 
structure under investigation, and a spring, which 
with the piston executed vibrations at a natural fre- 
quency typical of that structure. 

A foutth gauge used with success was based on the 
simple mechanics of the expelling of a projectile of 
known mass from a tube inserted in the side of the 
test structure. The distance over which the projectile 
was thrown was a measure of the pressure per unit 
area imposed on the interior walls by SBX. 

A modification of this fourth type was devised, but 
not extensively used. Essentially, it consisted of a 
car of known mass which moved with minimum fric- 
tion in a brass tube. Its velocity was determined by 
timing its transit through two electric contacts sepa- 
rated by a fixed distance and with a thyratron circuit 
supplied to start and stop an electric impulse-counter. 
This gauge was readily adapted to explosions of 
varying degrees. 16 

All the gauges gave trouble and were not always in 
agreement. It is believed that no new fundamental 
design was involved in any of them. 

6.6 FIELD PERFORMANCE 

Two large-scale demonstrations of the effective- 
ness of SBX were conducted: one against several 
wooden houses of varied ventage, and the other 
against a wooden vessel having two holds of about 
2,000 and 10,000 cu ft capacities. The more spec- 
tacular results were obtained using flour and the 
Lulu disperser-igniter on houses made available by 
operations of the Tennessee Valley Authority. 7 

For example, when a two-story building, in fair 
condition, measuring approximately 30,000 cu ft, and 
with windows boarded up to secure minimum vent- 
age, was attacked with a 95-lb bag of flour, and the 
standard Lulu detonated electrically, complete demo- 
lition resulted. Although a huge ball of flame en- 
veloped the collapsing building, no fire resulted. The 
view in Figure 6 was caught by the camera at the 
moment when the SBX had lifted the roof and was 
pushing out the walls. Figure 7 shows the interior of 
the building at the moment when the SBX is near its 
maximum effectiveness. The accompanying flames 
can be clearly seen. 

A similar trial on a solid wooden house, with a 
number of interior partitions and much ventage, re- 
sulted in a dangerous condition, but not demolition. 
Small Salex charges, located similarly in old dwell- 
ings, did less damage but provided sufficient sulfur 
dioxide fumes to render occupancy impossible, in 



Figure 6. Lulu — explosion in wooden house. 



Figure 7. Lulu — explosion in wooden house showing 
flame. 


spite of free ventilation, for some time after the ex- 
plosion. In a bunker or enclosed trench, the effective- 
ness of Salex is unquestioned. Whether such use 
would constitute chemical warfare is a matter for 
Service definition. 10 

As might have been expected, the results obtained 
in the well-enclosed hold of a derelict, but sound, 
wooden lugger were quite gratifying. A standard 
Lulu, detonated electrically, dispersed and ignited 
90 lb of flour with a resultant lifting of the deck 
throughout its whole length, splitting of the planks 
adjacent to the hull, and blowing away of the caulk- 
ing. The badly sprung and leaking hulk caught fire 
from the accompanying ball of flame and burned to 
the water line as it sank. Had the vessel been at sea 
it is believed that nothing could have saved it. The 
heaving deck and the escaping flames are shown in 
Figure 8. 5 



FAST BURNING INCENDIARY (FBI) 


39 



Figure 9. Ignition of a wooden hut by fast burning 
incendiary. 

It is apparent that the ratio of effective charge to 
volume of structure is much higher for FBI than for 
SBX, thus limiting the size of buildings which could 
be attacked in this way. 


Figure 8. Lulu — explosion in wooden ship. 


6.7 FAST BURNING INCENDIARY (FBI) 

The difference between a Slow Burning Explosive 
(SBX) and a Fast Burning Incendiary (FBI) is one 
of degree. In the former the presence of a ball of 
flame is unavoidable and of secondary importance, 
while in the latter it becomes the chief feature and 
the blast effect is repressed. That this could be easily 
accomplished by a suitable choice of conditions was 
demonstrated in England 18 and repeated in this 
country without difficulty 19 on small wooden struc- 
tures. The tactical limitations of FBI are similar to 
those already explored in Section 6.1, and it is not 
clear that FBI would be useful on any large scale as 
a filling for conventional bombs. However, as a spe- 
cial tool for attack by commando troops on particular 
combustible targets, it has much to recommend it, 
for the fire produced is so nearly instantaneous and 
the area set afire at one time so large that a successful 
defense is hard to imagine. 

The charge usually employed weighed about 20 lb 
for a wooden hut measuring 13 X 9 X 8 ft and con- 
sisted entirely of grade 0 magnesium and a small 
amount of magnesium turnings. Two pounds of gun 
powder were ignited by Bickford fuze. An almost 
silent flash resulted and a minor explosion, caused by 
the SBX effect, provided small openings which in- 
creased the draft. Five seconds after the burst, the 
entire structure was enveloped in flames and all the 
interior walls were afire. Four minutes later, the 
structure collapsed and in seven minutes was nearly 
entirely consumed. 18 Figure 9 shows the course of this 
experiment. 




Chapter 7 

SPECIAL REMOTE-FIRING DEVICES (NR-109) 


The simple devices described in this chapter were 
intended for deceptive use by guerilla groups, pa- 
trols, and small maneuvering forces, such as those 
employed by the Marines and OSS. They were in- 
tended to deceive the enemy as to the correct location 
of the group, and to trap him into revealing his own 
well concealed position. It was proposed that a num- 
ber of these devices (Bushmaster) be planted sur- 
reptitiously on one flank, and upon their actuation 
and the enemy’s presumed reaction, that an attack 
be made from the other flank. By the use of trip 
wires and conventional booby-trapping techniques 
the devices could also be set to cover the approaches 
to a defensive area. The usual usage visualized, how- 


plicity is shown by Figure l. 2 It consisted of a short 
length of gas pipe (7 to 8 in.) reamed at one end so as 
to chamber a cartridge (.45 caliber, although others, 
such as .22 or .30, would be equally feasible with the 
appropriate sized pipe). This served as the gun barrel 
of the device. The breech was provided by a pipe cap 
drilled so as to hold a time Pencil (Chapter 9) with- 
out its spring snout and primer. The barrel was pro- 
vided with a spring clip for attaching the device to 
small branches. When the time Pencil operated, its 
firing pin struck the primer in the base of the car- 
tridge, as would the trigger of a gun, with sufficient 
force for reliable firing. The inevitable recoil which 
shook the supporting branch and the sound of the 




Figure 1 . Single shot Bushmaster with wire clamp. 


ever, was with time delay actuation by means of the 
standard time Pencil (see Chapter 9). 4 

Originally, the requirement for Bushmaster was 
that: “It shall be small, portable, and self-actuating. 
It shall be capable of being installed by a single opera- 
tor in a bushy terrain and shall functional^, after a 
predetermined time delay, vibrate or move the 
bushes and intermittently fire live bullets in a pre- 
determined direction.” 

After early experiments with crude and heavy 
models, 1 a simple one-shot expendable unit was de- 
veloped which met these specifications and was put 
into limited procurement by OSS. Its extreme sim- 


live bullet were thought likely to mislead the con- 
cealed enemy and to draw his fire, thus revealing his 
own position to the users of Bushmasters in hiding on 
the flank. For intermittent fire, several Bushmasters 
with different colored time Pencils could be planted 
simultaneously. 

An attempt to produce a multiple-shot Bush- 
master based on this design failed, because all the 
time Pencils were the same color and in such weak- 
ened condition that the firing of the first delay dis- 
charged the others as well. It was necessary to de- 
velop an entirely original device and this took the 
form of the simple clamp shown in Figure 2. 


40 


SPECIAL REMOT-EFIRING DEVICES (NR-109) 


41 



Figure 2. Pencil clamp for M-3 submachine gun. 


A time Pencil, again minus its spring snout and 
primer, was attached by means of a simple screw- 
mount to the trigger guard of a standard M-3 sub- 
machine gun, so that the Pencil rested firmly against 
the trigger through a forked adapter. The gun was 
then mounted on a small tree. The firing pin of the 
time Pencil, upon striking the trigger, discharged the 
entire clip because of the constant and sufficient 
pressure exerted. 

For booby-trap use, the multiple-shot Bushmaster 
was modified by the substitution of a standard pull 
switch for the time delay. Production of all three 
types was successful. 3 







PART II 


SPECIAL FUZES 


In Part II of the Summary Technical Report of Di- 
vision 19, a few devices and several unsuccessful at- 
tempts to meet, by simple means, various field re- 
quirements, for initiating explosive and incendiary 
charges are discussed. The bulk of this work was con- 
cerned with time delay mechanisms, which probably 
will be of greatest value, for, as far as the writer is 
aware, research done in World War II on these small, 
simple, and very useful fuzes has not previously been 
gathered together. 

In Chapter 9, the work done with the existing time 
Pencil is described in detail. In Chapter 10, the suc- 
cessful development of a substitute for this delay, 
having improved qualities of temperature independ- 
ence and reproducibility, is discussed. Chapter 11 
describes the simple conversion of either of the above 
time Pencils to incendiary fuzes with silent operation. 
Chapter 12 gives the details of several clockwork de- 
lay mechanisms covering a range of timings between 
1 minute and 6 days, and, it is believed, that a previ- 
ously existing gap in American munitions was 
thereby filled. Chapter 13 describes the unsuccessful 
attempts to develop time delays based on a variety 
of physical and chemical phenomena, and one delay, 
the so-called AC Delay (Acetone-Celluloid), which 
was produced and used in small numbers. 


Chapters 8 and 14 give the results of work with 
two fuzes which were to be triggered by external 
forces at a preselected moment and which were not 
time delay devices. The first of these was a marine 
type known as the Concussion Detonator, which 
operated most successfully under water upon receipt 
of the explosive wave from an underwater explosion 
in the vicinity, thus allowing the simultaneous firing 
of many underwater charges. The other device, de- 
scribed in Chapter 14, was a radio-controlled switch 
intended to be operated by the receipt of a long signal 
with preselected characteristics. It was rendered safe 
against accidental triggering and provided with self- 
destructive and booby trapping features. 

Some of the observations made in Chapter 1 apply 
to the devices described in this part of the STR. 
They were on the whole very small, simple in opera- 
tion and construction, reliable, and best suited for 
use by individuals in special operations. These were 
naturally concerned mostly with demolition. The 
Service groups who expressed interest and followed 
this work of Division 19 were the Corps of Engineers, 
the Signal Corps, the Bureau of Ordnance, the Chem- 
ical Warfare Service, and OSS. 



43 





























. 




















Chapter 8 

SYMPATHETIC FUZE OR CONCUSSION DETONATOR 


8.1 INTRODUCTION 1 18 24 

In both ground and underwater demolition work, 
it was frequently desirable that several charges of 
high explosive be detonated simultaneously. This 
could be accomplished by linking charges with Prima- 
cord, an operation which was not recommended, be- 
cause of the time involved, the requirement of skilled 
personnel, and the clumsiness of the procedure. At 
the request of OSS, Division 19 personnel undertook 
the solution of this problem, basing their work on the 
development of a Sympathetic Fuze, which, on receiv- 
ing the shock wave set up by the explosion of one 
charge, would initiate another charge. Such a fuze 
was successfully developed. In its underwater appli- 
cation, it was of interest and value to the Corps of 
Engineers working at the Engineer Board at Fort 
Belvoir, Virginia, and at Fort Pierce, Florida, as well 
as to the Navy’s Underwater Demolition group. The 
problem of developing a Sympathetic Fuze for use in 
air was more difficult and the solution less satisfac- 
tory. Both types are described in this chapter. 

The former was entirely mechanical in operation, 
while the latter, in its most sensitive form, employed 
batteries for initiating the charge electrically. The 
marine type was ultimately produced in quantity by 
the Engineer Board and was known to NDRC as the 
No. 66 Concussion Detonator. A very similar model, 
differing only in minor points, was produced by OSS 
and known as the No. 67 Concussion Detonator. The 
operation of both fuzes depended on the blow given a 
firing pin by a bimetallic click diaphragm, when it 
was struck by the concussion wave sent through 
water from an exploding charge. 

Before these final models were perfected, prelim- 
inary fuze designs were made with frangible glass 
diaphragms. Section 8.2 describes this work in more 
detail. 

The division was also concerned with the arming 
mechanism for both marine and air fuzes. For the for- 
mer, the conventional salt block was improved upon by 
the development of the so-called Electrolytic Arming 
Disk (Section 8.4.2). For the latter, a somewhat sim- 
ilar arming was accomplished by forcing a constant 
viscosity liquid through a controlled orifice (see 
Section 8.4.3). 

The material presented in this chapter describes a 
new type of fuze, valuable for many underwater uses 


and of interest, also, for demolition above water. 
The production of both the No. 66 and No. 67 fuzes 
was sufficient to demonstrate unequivocally that the 
Concussion Detonator was a safe and producible item. 

8.2 PRELIMINARY DESIGN 18 24 

GLASS DIAPHRAGMS 

Through the courtesy of British liaison officers, the 
division contractor was provided with a Sympathetic 
Detonator constructed on an inertia principle and 
having a maximum range of about 70 ft. This device 
consisted of several brass tubes containing as the 
sensitive member, a heavy weight, balanced on a cone 
pin and susceptible to the slightest jar. The device 
approached an antidisturbance fuze in nature. It 
was considered not altogether sound. American at- 
tempts to alter this design, by the incorporation of a 
glass diaphragm into the firing mechanism, indicated 
at once that too great a strain would be placed on the 
glass member and that the fuze would have a shock 
sensitivity so great as to be unsafe to handle. The 
British fuze was already open to this criticism and 
was, moreover, most variable in its performance. 
This fuze is illustrated in cross section in Figure l, 18 
and it can be seen that its functioning depends upon 
carefully releasing support from a weighted pin, the 
point of which rests on the point of the trigger for 
releasing the firing pin. 

The principle of a frangible glass diaphragm, how- 
ever, became the basis of several designs, of which the 
three most important are described in Sections 8.2.1, 
8.2.2, and 8.2.3. 

8.2.1 Direct Release n - 18 

It was found possible to alter the standard release 
switch used by the Corps of Engineers so that its 
operation was restrained only by a piece of 0.006-in. 
glass of sq in., supported only on its rim. Against 
this glass window, rested the standard split-sleeve 
pull-pin release mechanism contained in its water- 
tight case. When submerged, this fuze failed to fire, 
only because of the very delicate support given the 
release mechanism by the thin glass window. The 
detonation of a high explosive charge within a radius 
of 50 ft at a depth of 5 ft or more was found to pro- 
duce a sufficient shock wave in the medium to break 


R ES IRK FE 


46 


SYMPATHETIC FUZE OR CONCUSSION DETONATOR 



Figure 1 . Inertia type Sympathetic Fuze. 


this thin glass window and to release the firing pin. 
The design, however, was faulty. Entry of water into 
the actual firing mechanism frequently prevented 
normal functioning, and the glass windows were very 
sensitive to accidental dropping. Although the fuze 
had an arming system which prevented its firing un- 
der such conditions, it was not a practical design. 

This prompted the development of further designs 
in which the firing mechanism did not rest directly 
upon the glass window and hence the glass was under 
no strain. 

8.2.2 Indirect Release 17 

By retaining the Army’s M 1 pull type firing device 
as the mechanical basis and the glass window as the 
shock sensitive basis, a fuze was designed which rec- 
tified these two objections. All moving parts were 
completely enclosed within a waterproof casing, and 
the release mechanism was restrained by a secondary 
device, rather than by the glass diaphragm. This 
secondary device consisted of a pellet of compressed 
salts which was held in a small wire basket located in 
a chamber directly beneath the frangible glass dia- 
phragm. So long as this salt pellet retained its 
strength, the release mechanism was unable to fire, 
but breakage of the glass window under water and 
entry of the water, resulted in almost instantaneous 
dissolution of the pellet and release of the firing 
mechanism. A suitable pellet made from Bromo- 


Seltzer had a weight of 40 mg, a diameter of 0.160 in., 
and a height of 0.156 in. Essentially instantaneous 
(that is, less than 0.5 sec) operation was obtained. 
In Figure 2, 17 illustrating this early model, the glass 
diaphragm is apparent and the small underlying wire 
container for the salt pellet appears. A standard salt 
block and pull ring provide safety. 



Figure 2. Indirect release, glass diaphragm type 
Sympathetic Fuze. 

8.2.3 Electrical Firing 14 24 

Because of the necessity for a watertight inner 
compartment for the moving parts, which in manu- 
facture might prove difficult, an electric model uti- 
lizing a simple sea cell was proposed. This consisted of 
a battery, lacking only the electrolyte for its opera- 
tion and providing 1 }/% amp at 6 v upon the addition 
of a suitable electrolyte such as sea water. It was 


METAL DIAPHRAGMS 


47 


proposed that in this design, upon the breaking of the 
glass window, sea water would be admitted to the sea 
switch, which, within a fraction of a second would 
deliver the electric current necessary to fire a stand- 
ard electric blasting cap. The practicability of this 
approach was demonstrated, but the design was not 
perfected because the Armed Forces believed that 
dependence upon water of definite salinity would 
limit the usefulness of this design. Also, a require- 
ment of 24-hour submersion in 20 ft of water was a 
definite handicap for any device of the glass window 
type, since it was found that glass, when under such 
continuous stress, would break after a given period, 
and that the glass of 0.006-in. thickness used in these 
three models would not withstand 15-ft pressure for 
that length of time. 

8.3 METAL DIAPHRAGMS 

8.3.1 Preliminary Designs 12 - 15 . *6 

It was suggested that the use of unequally stressed 
bimetallic diaphragms would have many advan- 
tages over glass ones, in that they would not be sus- 
ceptible to the breakage or strain imposed by long- 
submersion, and in operation would not allow the 
entry of sea water, thus making the design of a 
watertight fuze a simpler task. 

A number of such models based on the MI release 
type mechanism were constructed. The retention of 
the Ml device as the basis for design resulted in loss 
of simplicity, for it was found necessary to mount the 
metal diaphragm longitudinally to the firing pin and 
to transmit its energy through a trigger system. Ap- 
parently, this would be a complicated production 
matter. Largely because of this, the Ml release 
mechanism was abandoned as the basis for firing, 
but not before a number of experimental models had 
shown the soundness of the metallic diaphragm ap- 
proach. Using 2J4-in. Phosphor bronze disks in water 
having a depth of 20 ft, operational ranges approxi- 
mating 80 ft were obtained, when 2-lb charges were 
fired 3 ft below the surface. In many instances with 
fuzes similarly placed, operation at a distance of 
500 ft was obtained. The range depended upon the 
diaphragm stiffness, and Table l 15 illustrates this rela- 
tionship, as determined in small-scale experimenta- 
tion in air. In either air or water, orientation of the 
units with respect to the location of the charge ap- 
peared to be of minor importance. 


Table 1 . Relationship between range and diaphragm 
stiffness. 


Diaphragm stiffness in 
pounds per square inch 

Response range in feet 
from y 2 pound TNT 

9 

7 

4.5 

10 

0.75 

18 


A similar relationship between range and dia- 
phragm stiffness was found to exist when the fuzes 
were operated in water, although a 9-lb diaphragm 
was considered the minimum for safety in water be- 
cause of the requirement that the fuze not fire spon- 
taneously at depths of less than 20 ft. 

Several important basic designs resulted from ex- 
perience with this early fuze. It was learned that the 
metal diaphragm should not be tightly clamped at 
the edges, but should be seated on a rubber washer 
which would serve to exclude water from the interior 
of the fuze. Also, for protection, the diaphragm 
should be covered with a thin rubber membrane with 
a negligible spring or snap action. It appeared too 
that the total internal air volume in the fuze should 
be several times the volume change occurring when 
the diaphragm was deflected to the snap point, and 
provision was made for this air to travel freely around 
the edge of the metal diaphragm and equalize the in- 
ternal pressure with that of the very small air space 
between the metal disk and the rubber diaphragm. 
The snap diaphragm, in the unfired position, at no 
point should contact the trigger mechanism until it 
had been operated beyond the snap point. 

8.3.2 Fuze No. 66 3 and No. 67 1 

These devices differed from each other so slightly 
that they will be treated as a single fuze. They dif- 
fered from the early designs described in Section 8.3.1 
in that the Ml release mechanism was entirely aban- 
doned and a new firing system was adopted in which 
the firing pin, at right angles to the bimetallic dia- 
phragm, received directly the blow delivered by the 
snap of the diaphragm. Thus, the elaborate trigger- 
ing system, necessary in the previously used longi- 
tudinal design, was entirely eliminated and the desir- 
able features retained. Figure 3 illustrates the general 
features of both the final fuzes. 

The No. 66 fuze was provided with a 9-45 lb dia- 
phragm, whereas the No. 67 bore a 9-70 lb diaphragm 
of Type C Phosphor bronze. These figures mean that 
the disk would snap at a pressure of 9 lb per sq in. 
hydrostatic, and exert upon the firing pin 45 or 70 lb, 


48 


SYMPATHETIC FUZE OR CONCUSSION DETONATOR 



Figure 3. No. 67 Sympathetic Fuze. 


which was sufficient to give high detonation. All 
parts were made of die castings, with the exception 
of the firing pin, positioning and catch springs, the 
snap diaphragm, and synthetic rubber parts. 

Safety was provided by a salt block, which was lo- 
cated on the side of the trunk of the fuze. Dissolution 
of this caused a very lightly loaded positioning spring 
to displace a safety ball and to move the firing pin 
away from the snap diaphragm. When the firing pin 
had moved the proper distance, it was held in place 
by a catch spring fitting in a circumferential notch. 
This catch spring counteracted the force exerted by 
the positioning spring and placed the firing pin in an 
armed position ready to be struck by the snap dia- 
phragm. When the end of the firing pin had moved 
from the snap diaphragm into the armed position, 
the diaphragm was free from any elastic deformation. 
Sufficient pressure on its outer convex face would 
cause it to deflect and snap into a dished concave po- 
sition, thus delivering an impact directly against the 


firing pin, which, thus released from its catch spring, 
moved forward to fire the percussion cap. Actual 
photographic measurement showed that the time re- 
quired for this snap operation varied between 500 and 
2,000 microseconds. Figure 4 1 shows the details of 
the final design. 

The fuze weighed 123^ oz, including a watertight 
cap screwed over the soluble plug and a second cap 
closing the striker channel. It looked like a mush- 
room measuring 2}/ 2 in. in height and 2 % in. in out- 
side diameter. It was packed in hermetically sealed 
tear-strip tins 4 in. high and 3% in. in diameter, the 
total weight being 1 lb 2 oz, including the detonator 
and burster. 7 

8.3.3 Depth Compensation 12 > 13 

The design described in Section 8.3.2 is not com- 
pensated for depth and the Concussion Detonator 
may be expected to fire spontaneously when im- 
mersed to a depth sufficient to snap the diaphragm. 
In actual tests it was found that 20 ft was a safe limit 
for the 9-lb disk. Some work on a method of compen- 
sating such a fuze for depth was performed, but ad- 
vantage was never taken of this because the com- 
plexity and added expense were not considered justi- 
fied for the operations visualized by the interested 
Services. 

The simplest and most effective method of obtain- 
ing compensation would consist of merely trapping a 
volume of air behind the snap diaphragm. For ex- 
ample, a short, vertical, open-ended pipe with the 
diaphragm sealing its upper end, would provide 
nearly perfect compensation for a fuze in a vertical 
position. Operationally, the variable volume of air 
backing would have to be sealed or so arranged that 
it could not escape in any position of the unit, which 



Figure 4. 




END VIEW WITH COVER AND 
DIAPHRAGMS REMOVED TO 
SHOW CATCH SPRING 


Cross-sectional and end views of No. 67 Sympathetic Fuze. 


ARMING 


49 


would not be true of the above system. Sealing off 
with a thin rubber membrane would be a possible 
solution. 

Another possible compensator, a few models of 
which actually were constructed, involved the use of 
metallic bellows, which permanently soldered in 
place, offered no sealing, aging, or porosity problems. 
Such bellows, having 14 corrugations and a diameter 
of 2 in> were sufficient to compensate fuzes such 
as the No. 66 and the No. 67 to depths of approxi- 
mately 50 ft. However, this compensation involved 
increased size and it was not regarded favorably. Also, 
because of cushioning or back pressure, the sensitiv- 
ity of the diaphragm to the concussion wave might 
prove critical. For reasons such as these, compensa- 
tion was not further investigated, but a number of 
reports 12 - 13 - 15 - 18 - 24 give full details. 

8.4 ARMING 

8 . 4.1 Salt Blocks 

The use of salt blocks for the delayed arming of 
marine devices is very old, and a cursory study of 
available naval information indicated a great many 
varieties of salt blocks designed to give various tim- 
ings. The principle of operation, of course, depends 
upon the dissolution of the salt block in water to the 
point where the device is armed and ready to fire. 
In the case of the Concussion Detonator, it was not 
necessary that the device be fully armed before this 
point was reached, for the concussion wave traveling 
through the water may exert a force upon the metal- 
lic click diaphragm sufficient to cause firing of the 
device if the salt block has become weakened. 

The timing of the blocks used in the Concussion 
Detonators was the subject of many exhaustive 
studies by the Corps of Engineers, 3 - 5 by Maryland 
Research Laboratories, 10 - 21 and by the developer of 
the fuzes. 20 The Engineers conducted tests using 
actual salt blocks, in surf, in relatively still water, 
and in turbulent water at varying depths. The Mary- 
land Research Laboratories and the Holmes Electric 
Protective Company conducted tests in a tank under 
controlled conditions of temperature and circulation. 
All data agreed that turbulence of the ambient water 
could seriously affect the arming period and that ab- 
normal and undesirably short, safe arming times were 
obtained for fuzes in flowing water. For example, in 
water at 60 F flowing at the rate of only one knot, the 


safe time was reduced from 25 to 5 min, and the arm- 
ing time from 1 hour to 25 min. Such behavior was 
independent of the nature of the salt plug and, gen- 
erally, the addition of different salts and compression 
to different degrees did not influence this behavior. 
The effects of temperature, salinity, or position were 
minor. 

The block finally selected for use was composed of 
93.75 per cent sodium chloride, 6.00 per cent aspirin, 
and 0.25 per cent Prussian blue. It was molded under 
a total pressure of 2.17 tons. Attempts to rectify 
sensitivity to turbulence by alterations in the housing 
of the salt plug 10 were unsuccessful and no advantage 
was taken of them because of the lateness in the war 
of the development. It would appear that, if the 
Sympathetic Fuze is to be produced in the future, the 
salt block should be replaced by the Electrolytic 
Arming Disk, described in Section 8.4.2. 

8 . 4.2 Electrolytic Arming Disk 

This was intended for use in sea water and it would 
not operate satisfactorily in fresh water. Designed to 
utilize anode corrosion as a timing mechanism, it con- 
sisted of a disk-shaped primary cell mounted in a 
casing in contact with a spring-activated plunger in 
such a manner that the disk blocked the forward 
motion of the plunger. Its dimensions allowed it to be 
used as a replacement for the salt block in either the 
No. 66 or No. 67 model of the fuze. 

In essence the Electrolytic Arming Disk was sim- 
ilar to the sea cell mentioned in Section 8.2.3. The 
primary cell consisted of a perforated magnesium 
disk anode electrically short-circuited at its center to 
a silver-coated silver chloride disk of smaller diam- 
eter which formed the cathode. Upon immersion in 
an electrolyte, such as sea water, cell action caused 
the magnesium disk to corrode. Corrosion was con- 
fined to narrow annular rings around the spokes of 
the disk, by masking the remainder of the surface 
with enamel or lacquer. When the spokes corroded, 
the center portion of the disk was ejected by the 
spring, and the plunger moved forward to actuate the 
arming mechanism. Typical data for the performance 
of such a disk are given in Table 2. 23 

Table 2 shows the negligible effects of temperature, 
position of the cell, and water turbulence upon timing. 
It was this last feature which so recommended the 
Electrolytic Arming Disk. Unfortunately, however, 
it was sensitive to salinity, as well as to the thickness 
of the disk and the amount of exposed surface, but 


50 


SYMPATHETIC FUZE OR CONCUSSION DETONATOR 


Table 2. Performance of Electrolytic Arming Disk. 


Temperature 
degrees F 

Position of 
cell 

Time of opening in 
artificial sea water 

50.0 ± 0.5 

up 

21.4 minutes 


down 

23.9 


side 

21.5 



Avg 22.3 “ 

70.0 ± 0.5 

up 

18.7 minutes 


up* 

17.9 “ 


down 

19.8 


side 

15.4 


side* 

15.4 



Avg 17.4 

90.0 ± 0.5 

up 

15.4 minutes 


down 

13.7 


side 

13.7 



Avg 14.3 


* Cell kept in motion to simulate wave motion. All others in still water. 


none of these objections were considered insuperable. 
The change in salinity was not considered serious for 
conditions likely to be encountered in the ocean or 
along its shores, and the other objections could be 
controlled in manufacture. Table 3 22 shows how the 
time obtained varied with salinity. 


Table 3. Variations of time with variations of 
salinity. 


Per cent normal 
sea water 

Time of arming 
at 70F 

Position of cell 

114 

15.0 minutes 
14.5 “ 

up 

side 

100 

15.1 

up or side 

75 

20.2 

19.9 

up 

side 

50 

28.2 « 

28.8 “ 

up 

side 

25 

55.0 « 

50.3 « 

up 

side 

0 

12 hours 

11 

up 

side 


Figure 5 shows views of an assembled disk and its 
component parts. Because the cell was sensitive to 
moisture, it was kept tightly sealed, until the moment 
of use, by a b^ass cap which was unscrewed when the 
Sympathetic Fuze was placed. Subject to the limita- 
tion of deterioration caused by atmospheric corro- 
sion, the Electrolytic Arming Disk seemed to be a 
significant improvement over the conventional salt 
block. It could be made, of course, for any desired 
timing. 





Figure 5. Assembled and exploded view of Electrolytic Arming Disk. 



PERFORMANCE IN WATER 


51 


8.4.3 Silicone Arming Device 8 for 
Air Operation 

For air use, neither the salt block nor the Elec- 
trolytic Arming Disk would suffice, because both re- 
quired water for their performance. Work on an arm- 
ing mechanism suitable for air operation was under- 
taken, since many devices could profit by such a de- 
velopment. The result was a dash-pot type of delay 
suitable for use with the No. 66 or No. 67 Sympa- 
thetic Fuze. It consisted of a piston pushed by a 
spring against a neoprene cup. The cup contained a 
silicone fluid which leaked through a capillary on the 
top of the device. With a suitably sized orifice, 10 min 
were required for the piston to move sufficiently to 
free the ball in the Sympathetic Fuze, thus arming it. 
The remarkable new silicone oils seemed especially 
suitable, because of the independence of their vis- 
cosity to temperature. Careful control of spring ten- 
sion and orifice size would be required in manu- 
facture. 

There was a possibilitj^ that a volatile plug might 
be found which would function in air in a manner 
analogous to the salt plug in water. A search of chem- 
ical literature and appeals to a number of industrial 
laboratories failed to locate any substance which 
could be useful for this purpose, available in quantity, 
inexpensive, sufficiently volatile, and odorless. 

8.5 PERFORMANCE IN WATER 

Because of the incompressibility of water, the pres- 
sure wave set up by the explosion of underwater 
charges is large and extends over a considerable dis- 
tance. Fortunately it was not necessary to determine 
the exact relationship between weight of explosive, 
pressure wave, time, and distance, for this had al- 
ready been done. 4 From data of this sort, it seemed 
that the Sympathetic Fuze could be counted upon 
for reliable actuation by charges as small as 2}/£ lb at 
distances of 50 to 100 ft. Larger charges at greater 
distances could also be expected to give reliable 
functioning. 

A number of tests conducted by the Engineer 
Board 3 and confirmed by other investigators 6 
showed clearly that the range obtainable was a func- 
tion of the weight of charge, the loading of the click 
diaphragm, and the type of bottom. It appeared to be 
independent of the type of high explosive used, no 
noticeable difference being obtained from charges of 
Composition C2, TNT, or Torpex. As might have 
been expected, the range was increased by increasing 


the depth of both charge and fuze, for the charge did 
not then expend any considerable portion of its 
energy in the air or against the bottom, as it would 
in shallow water, and the fuze was close to its spon- 
taneous firing point because of hydrostatic pressure. 
It was found that the safe effective range for 100 per 
cent functioning, using a 9-70 lb bimetallic dia- 
phragm, was 75 ft at a depth of 3 ft, and 100 ft at a 
depth of 5 ft. In all cases, standard charges of 2J/£ lb 
of high explosive were employed. The safe effective 
range was obtained over a mud bottom, and it could 
be expected to be doubled over a hard, sandy sea bed. 
Data of the sort usually obtained are given in Tables 
4 and 5. Table 4 3 indicates the relationship between 
range and depth of water using a 23 ^-lb charge with 
both charge and fuze at the same depth. Table 5 6 


Table 4. Relationship between range and depth of 
water. 


Depth of water 

Range 

in feet 

in feet 

2 

40 

4 

90 

8 

200 


indicates the difference between mud bottom and 
sand bottom with charge and fuze located at various 
depths using 9-70 lb diaphragms and a total water 
depth of 20 ft. 


Table 5. Variation between mud bottom and sand 
bottom. 


Depth of charge and 
fuze in feet 

100% firing distance 
of fuze from charge in feet 
Mud bottom Sand bottom 

23^ 

55 

105 

3 

75 

125 

4 

90 

165 

5 

115 

200 


The above tables have assumed that the Concus- 
sion Detonator and the actuating charge were at 
identical depths. Figure 6 1 indicates the beneficial 
effect of increasing the depth of the actuating charge, 
regardless of the depth at which the Concussion De- 
tonator is located. It is believed that this is instruc- 
tive for many types of marine use. 

The proximity of large objects which might tend to 
absorb the concussion wave, as would be expected, 
materially reduced the range, thus, for example, fix- 
ing the Concussion Detonator to a charge adjacent 
to a vessel resulted in appreciable loss in range and 


52 


SYMPATHETIC FUZE OR CONCUSSION DETONATOR 


sensitivity. In this case, the vessel could be consid- 
ered as a large volume of air tending to cushion the 
shock wave. For work against underwater obstacles 
this consideration was usually unimportant. 19 

8.6 PERFORMANCE IN AIR 

8.6.1 Metallic Diaphragm Type 9 

Table 1 indicates that fuzes of the No. 66 and 
No. 67 type could be used for the detonation of 
charges in air utilizing the shock wave produced in 
that medium. Because air is tremendously more com- 
pressible than water, such shock waves can be ex- 
pected to have the necessary force only over much 
shorter ranges, and hence operation of the marine 
type fuze in this way, while possible, cannot be ex- 
pected to equal the ranges shown in Table 5. Results 
obtained when plastic explosive or TNT was de- 
tonated in air in an open grass-free field with the 
metal diaphragm facing the sky are given in Table 6. 

From this data it appears that there was little dif- 
ference in the effectiveness of the two explosives 


Table 6. Response range of Sympathetic Fuze in air. 9 


Actuating charge 

Response range in feet 

I lb TNT 

28 

1 lb TNT 

34 

2 lb TNT 

37 

lib C3 

27 

li lb C3 

33 

21 lb C3 

50 

4i lb C3 

60 

9 1b C3 

75 


tested and that the effective operating range was not 
greatly increased by increasing the actuating charge. 
In special cases for short range work, particularly 
within confined structures where there are few ob- 
stacles separating the actuating charge from the Con- 
cussion Detonator, the latter may be useful, and the 
cumbersome and time consuming procedure of hook- 
ing together multiple charges with Primacord may be 
avoided. If this type of operation were an important 
one, it would appear that the development of a new 
fuze for the purpose would be preferable. Such a fuze 
in a preliminary form was devised and is described in 
the following section. 



RANGE FT (S) 

Figure 6. Effective range of No. 67 Sympathetic Fuze at varying depths of both fuze and actuating charge. 



MANUFACTURE AND QUALITY 


53 



Figure 7. Operation of Sympathetic Fuzes in open water. 


8.6.2 Reed Type 9 

Assuming that the use of batteries was allowed, a 
device was constructed which depended upon the 
closure of an electric circuit, containing a squib or 
electric blasting cap, by the action of the concussion 
wave from an actuating charge. It consisted simply 
of a reed connected to one terminal of a flashlight 
cell. Connection of the other cell terminal to a bind- 
ing post on a contact plate was through an electric 
detonator to the reed clamp. An inward deflection of 
%6 in- caused the reed to touch the sloping contact 
plate, and, because of friction, to adhere to it long 
enough for an intense electric impulse to pass through 
the squib. The sensitivity of this type of Sympathetic 
Fuze was found to depend on the stiffness and length 
of reed, the clearance between the edges of the reed 
and the edges of the opening in the fuze, the shape of 
the contact plate, clearance between it and the reed, 
and lastly the free volume of the fuze body and sound 
absorbing properties of its interior. Either hard 
berylium-copper foil or similar aluminum foil of 
0.006-in. thickness in a free length of 2 in. formed a 
suitable reed. Its separation from the contact plate 
was close to 0.005 in., the latter being at a constant 


slope of approximately 10 degrees. It was upon these 
features that the sensitivity of the fuze depended. 
Such a fuze seemed to respond to the relationship 
R ~ Q*, where R is the operating distance when 
charge Q is detonated. Using the same actuating 
charges given in Table 6, the reed type under identi- 
cal conditions gave ranges of 40 ft, 60 ft, 75 ft; 50 ft, 
60 ft, 75 ft; 120 ft, and 150 ft, 9 averaging nearly twice 
that of the metal diaphragm type. 

8.7 MANUFACTURE AND QUALITY 1 2 7 

NDRC semi-production, together with independ- 
ent Engineer Board production on a larger scale, 
showed that the Sympathetic Fuze in either model 
No. 66 or No. 67 was feasible to manufacture. Die 
castings were used throughout with the exception of 
the firing pin, positioning, and catch springs, the 
snap diaphragm, and synthetic rubber parts. Toler- 
ances were determined by many tests to be well 
within good manufacturing practice. No difficulty 
was encountered in obtaining uniform metallic dia- 
phragms, and the chief trouble which arose was 
caused by the variability of the arming time when 
salt blocks were used. 




Chapter 9 

PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 


9.1 INTRODUCTION 1 30 46 56 

In Part I of this volume, frequent reference has 
been made to the use of time Pencils for delayed- 
action firing of several devices including the rocket 
launcher (Chapter 1), the oil slick igniter (Chap- 
ter 2), the Spigot Mortar (Chapter 5), and special 
remote-firing devices (Chapter 7). The general use- 
fulness of short and reliable time delays in clandes- 
tine and special operations is, therefore, apparent 
and does not require amplification here. 

In most of the cases mentioned above, the time 
delay was employed to initiate an explosive charge or 
weapon and, in the form suitable for this purpose, 
was known in the United States as the Signal Relay 
American Model 3 (S.RA-3). The British originators 
of the device had given it the code name Signal Re- 
lay. When it was put into American production, the 
distinction was made between SR and SR A, and, 
since American production went through several 
changes, SRA-3 represents the third and final model, 
12,000,000 of which were ultimately manufactured. 
In the case of the oil slick igniter, the time Pencil 
was slightly modified to accomplish the initiation of 
an incendiary charge rather than an explosive charge. 
This was done by substituting a matchhead ending 
in place of the primer cap ending of the standard 
SR A and is the subject of Chapter 11. 

A device, of such general usefulness was required in 
such a quantity as to warrant tremendous produc- 
tion, and a careful study of all factors which might 
affect the performance of the individual device and 
the reproducibility of batches of devices was neces- 
sary. This investigation was undertaken by Divi- 
sion 19 and two contracts were primarily concerned 
with many minor points for manufacturing, develop- 
ing a number of alternative parts, and large-scale 
testing of the final products under carefully con- 
trolled conditions. The division cooperated for nearly 
two years with the interested Services (the OSS, their 
British liaison officers, and the Corps of Engineers) 
and with the manufacturers, so that the quality of 
SRA-3 steadily improved and the device, as finally 
produced, was nearly perfect for the given system. 
As will be clear below this system was inherently 
weak in that it depended upon complicated electro- 
chemical and chemical reactions and by nature was 
greatly affected by temperature change and subject 


to the most unpredictable variations due to appar- 
ently minor changes in manufacturing procedure. 

Sections 9.3 through 9.10 of this chapter analyze 
the different parts of the Pencil and the discoveries 
made with reference to them, while Section 9.11 in- 
dicates the test procedures developed for accurately 
determining the quality of production. The ultimate 
performance to be expected of the device is given in 
Section 9.12. 

As a time delay, the SRA-3 covered the period be- 
tween approximately 10 min and 11.5 hours at an 
ambient temperature of 70 F. This range of timing 
was achieved through the use of six models having 
nominal values, judged convenient for field usage. 
The limitations of reproducibility and temperature 
coefficient, however, tended to vitiate this system, so 
that a man in the field was required to use very good 
judgment in selecting a particular model for a given 
operation under given ambient conditions. 

This stimulated, on the part of Division 19, a 
search for an improved system on which to base a 
Pencil time delay, and resulted in the so-called 
Mark II Pencil which is the subject of Chapter 10. 
It is believed that this development, while successful 
in producing a Pencil superior to the Mark I (SRA-3) 
in reproducibility and temperature coefficient, would, 
in practice, not supplant the Mark I for ordinary 
field use because of expense and positional require- 
ments. Hence, the importance of this chapter in re- 
cording the numerous points discovered by the divi- 
sion’s research into the Mark I Pencil. It is not be- 
lieved that, should the Services require a time delay 
having simplicity, cheapness, and reliability, arty 
great improvement could be made over the SRA-3 as 
finally produced. 

9.2 DESCRIPTION AND OPERATION 1 52 

Two models of the Pencil were manufactured dur- 
ing World War II by the OSS and the Corps of En- 
gineers. First production by the latter group was 
essentially complete prior to the work of the division 
and was comparable with the SRA-1, produced by 
OSS and soon supplanted by SRA-2 and SRA-3. The 
final production by the Corps of Engineers was com- 
parable with the SRA-3. The basic difference be- 
tween the SRA-3, which was the product of the OSS, 
and the firing device, delay type, M-l of the Corps 




54 


TENSION WIRE 


55 


of Engineers was in the ending, which consisted of a 
primer cap with spring snout, in the first case, and a 
standard waterproof primer and detonator assembly, 
in the second. These two devices will be treated as 
one and the description which follows is of the final 
SRA-3 production. 

The Pencil was of the simplest construction. It con- 
sisted of a striker held against a compressed spring by 
a tinned iron music wire loaded under tension. This 
wire passed through a chamber containing a glass 
ampule filled with a copper chloride solution. Manual 
crushing of this ampule was possible, since the cham- 
ber was constructed of a thin copper tube. Upon be- 
ing crushed, the ampule liberated its contents, which 
were absorbed in cotton wads, or wicks, located at 
either end of the chamber in close contact with the 
iron wire. A reaction was thereupon initiated which 
resulted in the erosion of the iron wire. In time, the 
strained wire would reach the breaking point, where- 
upon the striker would be forced forward by the com- 
pressed spring against the primer, initiating it and, 
hence, an explosive charge through the conventional 
detonator system. Figure 1 illustrates the SRA-3 in 
cross-section. The various components and their in- 
terrelation are made clear. 

Reference to this figure shows a number of parts 
which received particular attention in the research 
work of the division. These parts are the tension 
wire, the ampule solutions, the wicks, the reaction 
chamber, the spring, the primer, and the plunger. 
Each of these is discussed in a section below. The 
other parts not mentioned appeared to have no un- 
predictable effects upon the performance ol the Pencil 
and, hence, are not discussed here. Their specifica- 
tions could apparently not be improved upon. 

The timings provided by different models of the 
SRA-3 resulted when different solutions were placed 


in the glass ampule. These solutions, for convenience, 
were given names based on primary colors, and the 
different models of the Pencil were distinguished 
from one another by the corresponding color of the 
safety strip, thus the six models of the SRA-3 were 
known as Black, Red, White, Green, Yellow, and 
Blue, in order of increasing time from 10 min to 
11.5 hours. Exact timings for various temperatures 
will be found in Section 9.12. 

In field use OSS specified that two Pencils should 
be employed for any given operation, and this pro- 
cedure was strongly urged for the Corps of Engi- 
neers. From a statistical viewpoint, the use of two 
Pencils gave a reliable and predictable timing, and 
the figures quoted in time-temperature charts pre- 
pared by Division 19 were based on this usage. When 
possible, therefore, an individual employing time 
delay Pencils would connect two of them to the de- 
vice or charge to be initiated, and, with the safety 
strips still in place, manually crush the reaction 
chambers containing the ampules. The safety strips 
then would be removed and a quick departure made. 
In this way, the occasional premature, which might 
be encountered on crushing the reaction chamber, 
was rendered harmless. 

9.3 TENSION WIRE 

9.3.1 Substitutes for Music 

Wire 2 7 27 

When the specifications for the SR were received 
from England and applied to American production, 
every attempt was made to duplicate in this country 
the exact details of the British device. One of the 
most difficuT parts of the SR A to copy was the ten- 
sion wire, a hardened 14-mil iron music wire having a 




Figure 1 . Cut-away view of SRA-3, actual size exterior. 



56 


PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 


protecting tin coating. In the SRA-3, the diameter of 
the wire was changed to 20 mils, but otherwise it re- 
mained unaltered throughout the war, although con- 
siderable work was done by the division to find an 
improved steel wire and an improved procedure for 
protecting it. Both nichrome and stainless steel wire 
had very high mean deviations and therefore were 
not considered further. 6 More encouraging results 
were obtained with a softer and thicker (42 mil) wire, 
and very encouraging results with standard 20-mil 
wire when coated by hot dipped galvanizing (see 
Section 9.3.4). No experiments were performed to 
show the exact relationship between operational time 
and chemical composition of various wires. Further 
study along these lines might be profitable, since it 
was found difficult in practice to obtain from wire 
manufacturers uniform coils having an elemental 
analysis which could be reproduced from one to an- 
other. The effect of these minor elemental variations 
was never explored. 

9.3.2 Tensile Strength 4 7 

A study of the variation in tensile strength of the 
wire used in production, both between coils and 
within coils, yielded no significant result in the case 
of the electrogalvanized wire, ultimately recom- 
mended, but did indicate a significant difference in 
the case of the tinned music wire used in production. 
For example, the variation in average breaking 
strength along a coil of 14-mil production wire might 
be: 62.1 lb at one end, 61.3 lb in the middle, and 
59.8 lb at the other end. Further data would have to 
be obtained before it could be said that this variation 
was significant, but it appeared to investigators that 
it might be. Thus, further work would be indicated, 
if the tinned music wire originally specified were to 
be used in future production. 

The ultimate tensile strength of such wire was 

391.000 lb per sq in., in contrast to the value of 

102.000 lb per sq in. obtained with 30-mil electro- 
galvanized low-carbon steel wire recommended by 
the division. Whether a high or low tensile strength 
wire was preferable is still a moot question. 

9.3.3 Internal Structure 

In the hope that variations within and between 
coils of production wire might be detected by simple 
analytical procedures, the microstructure of the 


tinned music wire was examined. 14 The results were 
entirely negative. No correlation appeared to exist 
between microstructure and performance, since the 
crystal grains were so seriously distorted. 

9.3.4 Surface Treatments 24 - 25 - 26 - 29 

As already stated, the original specifications called 
for a tinned music wire but the use of tin for the pur- 
pose of protecting iron wire was repeatedly ques- 
tioned on sound scientific grounds by the division. 
It is well known that, in all common media, iron is 
anodic with respect to tin and hence the tin, unless it 
forms a perfect coating over the iron wire without 
pinholes, will actually facilitate its erosion by the 
atmospheric conditions of storage. That this was a 
very serious problem in the field became apparent 
when it was learned that tremendous stores of the 
original British production had shown over 50 per 
cent failure after one year’s storage in the humid, 
tropic conditions of India. The work of the division 
clearly showed that much better protection for iron 
wire was provided by a thinner coat of electrogalva- 
nized zinc, and the recommendation for a change from 
tinned wire to zinc-coated wire was eventually ac- 
cepted and written into the specifications. However, 
prior to the use of this improved wire, production 
ceased because of the ending of the war. 

Application of zinc by hot dipping, the procedure 
used for tinning, was definitely inferior. The maxi- 
mum thickness of zinc that could be used with the 
specified solutions of all colors without causing 
secondary difficulties was 1.6 X 10~ 5 in., a figure 
which was easily obtained by a simple laboratory 
procedure. Coils of wire thus protected were made 
for experimental purposes and were used in the sub- 
sequent development of the Mark II Pencil (see 
Chapter 10). It was also shown that, for uniform per- 
formance in the Pencil, the tension wire should be 
either completely free of grease or covered with a 
continuous oil film. 24 

A number of other treatments, including beeswax 
coating, Parkerizing, and protective oxidation, were 
all inferior to electrogalvanizing. It is interesting that 
in a Russian time Pencil, which was provided for 
analysis, a 16-mil bare spring wiring had no coating 
whatsoever. It was the opinion of the research work- 
ers in the division that this was preferable to the tin 
wire specified by the American Services but inferior 
to the electrogalvanized wire eventually recom- 
mended. 


SOLUTIONS 


57 


9.3.5 Wire Variations 3 23 

It was clearly demonstrated that commercially 
obtainable tinned music wire, as delivered to the 
Pencil manufacturers in 4-lb coils, showed consider- 
able variation both within and between coils. 
Whether this was caused by the inevitable variation 
in tinning or was inherent in the wire was difficult to 
say. At any rate, it represented a serious hazard to 
reproducibility and eventually necessitated testing 
each coil in the completely assembled Pencil before 
that coil could be used for production. Apparently, 
this could be corrected by electrogalvanizing treat- 
ment, and, should production of such a device be 
undertaken in the future in more than one country 
or locality, all manufacturers should be provided 
with wire from a single commercial source. Every at- 
tempt to secure a wire identical with British wire, 
from American manufacturers, resulted in failure, 
and the British themselves were unable to reproduce 
the wire previously used. 

9.4 SOLUTIONS 

9.4.1 Solution Analysis 

Absolute Chemical Analysis 33 37 

As part of the original British specifications, a 
chemical method was provided for the manufacturer 
to prepare the ampule solutions to the tolerances 
specified and determined essential for reproducible 
Pencil functioning at given times. For the Black and 
Red Pencils having normal timings of 10 and 20 min 
at 70 F, no difficulty was encountered because the 
ampule solutions contained only water and hydrated 
cupric chloride of analytical quality. The other four 
colors, however, contained a third component, 
namely, glycerol. This was added to increase the vis- 
cosity and to reduce the rate of chemical reaction, 
and thus to provide longer timings. Table 1 26 gives 
the exact compositions specified for the different 
colors. 

The absolute chemical determination of the per- 
centage of glycerin and of copper in a solution pre- 
pared for these colors was extremely difficult. Fol- 
lowing the original British directions, variable re- 
sults were obtained in different laboratories in this 
country. This necessitated a study of the method, for 
the performance of the Pencils was based entirely on 
an accurate knowledge of the composition of the 


Table 1. Composition of various colors of Mark I 
Pencils. 


Color 

% CuCl 2 • 2H 2 0 

% Glycerol 

% Water 

Black 

13.86 


86.14 

Red 

37.76 


62.24 

White 

10.38 

48.8 

40.8 

Green 

35.05 

38.2 

26.7 

Yellow 

33.16 

46.1 

20.7 

Blue 

10.13 

72.2 

17.7 

Revised Green* 

24.95 

47.3 

27.5 

Revised Yellow* 

22.70 

55.7 

21.6 


* These compositions were deduced as a result of the study mentioned 
in Section 9.4.6 and would be expected to give improved performance 
regarding reproducibility and temperature coefficient. 


ampule solution. Eventually, a satisfactory pro- 
cedure was devised depending upon the determina- 
tion of the cupric ion by titration with sodium thio- 
sulfate, followed by long digestion of the solution 
with an excess of potassium dichromate, and by 
titration of the remaining oxidants (unused dichro- 
mate and cupric ion). A simple calculation there- 
upon provided the original composition of the solu- 
tion in terms of glycerol and copper chloride. These 
manipulations required so much analytical skill and 
expenditure of time as to be of little value to the 
ordinary manufacturer, and a more convenient and 
accurate analytical procedure was necessary. Two 
such procedures were devised and are described in 
the following two sections. Both of them had ac- 
curacy equal to or superior to the absolute chemical 
determination and were preferable in all other re- 
spects. 

Specific Gravity and Glycerol Content 10 ’ 13 ’ 17> 19 - 31 

Both British investigators and the division’s re- 
search laboratories did considerable work with a sys- 
tem of analysis based upon determination of the per- 
centage of copper chloride by the thiosulfate titration 
already mentioned and by specific gravity. Determi- 
nation of the specific gravity of a solution was a sim- 
ple, accurate, and quick procedure. Two reports were 
issued by the division’s contractor 10 ’ 13 which 
showed clearly that the procedure was suitable for 
the use by manufacturers, with the result that it be- 
came part of the specifications as written by OSS and 
the Corps of Engineers. 

The White and Blue solutions, which contained 
nearly 10 per cent copper chloride hydrate, were 
found to fit an empirical equation as follows: spe- 
cific gravity (25 C/25 C) = 0.9747 + 0.0100 (%Cu 
C1 2 -2H 2 0) + 0.0284 (% glycerol). Table 2 10 shows 
the accuracy of the method. 


58 


PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 


Table 2. Relationship between specific gravity and 
glycerol content. 


Specific 

gravity 

25C/25C 

% Glycerol % Glycerol 
dichromate empirical 
% CuCk • 2 H 2 O method equation 

1.2086 

9.52 

48.9 

48.83 

1.2807 

9.52 

74.0 

74.23 

1.2278 

9.74 

54.7 

54.82 

1.2262 

10.26 

52.7 

52.43 

1.2664 

10.23 

66.7 

66.69 

1.2343 

10.77 

53.5 

53.49 


A family of curves was determined experimentally 
which fitted the above equation within the limits of 
error of the experiment. The data was presented in 
charts relating the specific gravity to the percentage 
of glycerol for varying concentrations of copper chlo- 
ride, and the specific gravity to the percentage of 
copper chloride for varying percentages of glycerol. 
Similar curves were determined for the Green and 
Yellow solutions in which the percentage of copper 
chloride was between 32 and 37. Unfortunately, in 
these higher concentrations no empirical relationship 
expressable by an equation could be discovered. It 
was clear that the curves were not parallel, as in the 
earlier case, and that they were not linear. Neverthe- 
less, the charts were sufficiently useful to be included 
in the specifications. 

So that this data might be more useful to manu- 
facturers, solutions prepared by weight and carefully 
checked by absolute chemical analysis were then 
compared with the specific gravity data already men- 
tioned, and acceptance area charts were drawn for 
each of the solutions relating specific gravity to per- 
centage of copper chloride. It was only necessary for 
the manufacturer to prepare a solution as accurately 
as possible by weight, then to determine its copper 
content and specific gravity, and by the use of ac- 
ceptance chart to find whether the resulting point 
lay within the area specified. Eventually producers 
in both Britain and the United States used this pro- 
cedure. 19 

A sample chart for White solutions appears as 
Figure 2. 

Refractive Index and Glycerol Content 33 - 43 

A physical measurement, rivaling the determina- 
tion of specific gravity in ease and exceeding it in 
speed, was the determination of the refractive index 
by the Abbe refractometer (see Table 3). 

Application of this procedure to the four solutions 
containing glycerol showed clearly that the method 



9.90 10.00 10.10 10.20 10.30 10.40 10.50 10.60 10.70 


PER CENT CuCL 2 -2H,0 

Figure 2. Acceptance chart for White solution. 

was sufficiently precise and compared favorably with 
the specific gravity method in ease of operation, size 
of sample, and speed. Charts were prepared showing 
the relationship between the refractive index and the 
percentage of glycerol for solutions containing known 
percentages of copper chloride. Acceptance charts 
also were constructed. Unfortunately, the refracto- 
metric method was not put into use, largely because 
of the unavailability of suitable refractometers. In 
any future production, and certainly in any large 
research program, the refractive index method would 
probably be preferable to any of the other analytical 
procedures. 


Table 3. 35 Analysis of per cent glycerol by re- 
fractometrv. 


Color 

range 

% Glycerol 
by synthesis 

% Glycerol by 
refractive analysis 

Refractive 

index 

Blue 

75.1 

75.1 

1.4603 

Blue 

73.05 

73.55 

1.4582 

Yellow 

32.95 

33.75 

1.4512 

Yellow 

41.3 

42.1 

1.4656 

Green 

46.9 

47.3 

1.4746 

White 

52.55 

53.1 

1.4263 

White 

50.8 

51.3 

1.4235 


Conductometric Analysis 53 

British work on a further analytical basis com- 
pared the resistance of solutions at 1,000 cycles in a 
special cell with that of permanent standards. As in 
the three previous methods of analysis, the conduct- 
ance was used with an iodometric thiosulfate de- 
termination of copper. Analysis for the percentage of 
glycerol was thereby possible. The specific conduc- 
tivity was measured in a bath thermostatically con- 
trolled to a temperature of 25.0 ± 0.2 C and it ap- 
peared that the control of temperature of the solution 
was the limiting factor in the usefulness of the 


SOLUTIONS 


59 


method. The solutions containing glycerol, having a 
very high viscosity, did not reach a constant temper- 
ature in a reasonable length of time ; and, because of 
the variation in conductance per degree C was ap- 
proximately 5 per cent, the method was criticized on 
the basis of practicability, especially in view of the 
ease and simplicity of the specific gravity and re- 
fractive index procedures already mentioned. As in 
the other cases, acceptance area charts and graphs 
relating conductance to percentage of glycerol for a 
constant percentage of copper chloride were pre- 
pared. 

9.4.2 Optimum Volume 8 9 

In the early days of SRA production, the impor- 
tance of the volume of solution contained in a Pencil 
ampule was not appreciated. Moreover, manufactur- 
ers declared that the manufacturing difficulties of 
making ampules of the size required for the reaction 
chamber of the Pencil was a sufficiently difficult task 
without the added imposition of a complete, or nearly 
complete, filling. The SR production in Britain was 
based on an ampule containing somewhat less than 
0.6 cc of solution; the volume of the early American 
products (SRA-1 and SRA-2) in many cases did not 
exceed 0.4 cc. It was not long before tests showed 
that this decrease in volume was having serious 
effects upon the reproducibility of the American 
product. 

A study was thereupon undertaken in which the 
volume of the ampule solution was continuously var- 
ied between 0.3 and 0.8 cc. The data clearly showed 
that 0.7 cc should be the minimum volume of solution 
used in any case. With less than 0.7 cc, there were in- 
dications that two reactions occurred : first, the action 
of cupric ion on iron wire, and, secondly, the action of 
cupric ion on copper forming cuprous ion, which in 
turn either precipitated or reacted with iron. Because 
the latter reaction was much slower than the former, 
for Pencils having a low ampule volume, an extensive 
period of time would be required for complete re- 
action. Moreover, the time required for the ampule 
solution to be soaked up by the wicks appeared to be 
a function of the volume. A study of Figure 3 clearly 
illustrates this point. 

The recommendation to increase the ampule vol- 
ume was accepted by the Services and, ultimately, by 
the manufacturers, and resulted in greatly improved 
performance of the SRA-3. It was interesting to note 
that the Russian time Pencil had a volume of 0.71 cc. 



VOLUME OF SOLUTION IN CC 

Figure 3. Effect of solution volume on timings. 


9.4.3 Off-Color Solutions 16 34 

The assembly of the Pencil by hand gave an op- 
portunity for observing the real color of the ampule 
solutions as they were inserted. This should not be 
confused with the color of the ampule specified for a 
given time. Since all the solutions contained copper 
chloride in varying amounts, they were the char- 
acteristic blue-green color of that salt, except for the 
White ampules, which were so nearly colorless as to 
require the addition of a trace of organic dye for their 
detection. 

Operators on the assembly line frequently observed 
that the real color of the solutions varied from one 
ampule to another in the same batch. Upon instruc- 
tion, they removed these off-color ampules and these 
were subsequently submitted to analysis. Frequently 
ampules of this type whose shading was not constant 
showed gross variations from the specifications for 
either glycerin or copper chloride content. Therefore, 
the practice was established of discarding all such 
ampules. The source of the difficulty appeared to be 
in the ampule filling machines which, when started 
after a rest period, delivered variable concentrations 
for a short time. 

In future production this point could be observed 
easily. 

9.4.4 Diluents Other Than Glycerol 

Because the determination of glycerol was so diffi- 
cult (see Section 9.4.1), attempts were made to dis- 
cover other chemicals which might replace glycerol 
and which, in addition, might give lower temperature 
coefficients to the resulting solutions. Investigations 




60 


PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 


of a number of water soluble alcohols, polyhydroxy 
alcohols, and sugars as substitutes for glycerol was 
undertaken but without success. The only significant 
discovery was that the replacement of glycerol by 
n-propyl alcohol 2 gave improved performance with 
Blue and Yellow timings. 

Here a new difficulty arose in that the solution was 
too volatile for direct replacement. Methods of seal- 
ing the solution within the reaction chamber were 
devised but nothing beyond semi-production was 
ever undertaken. 6 Acetic acid, ammonium hydroxide, 
diethyleneglycol, ethyl lactate, ethyl acetate, and 
dioxane were tested without satisfactory results. 

An attempt to increase the maximum timing of the 
SRA to days resulted in the development of a 
solution containing diethylenetriamine, but this solu- 
tion proved so critical to the minutest change in con- 
centration that it was discarded as unsatisfactory. 
Figure 4 clearly shows how minor variations in the 
percentage of copper chloride could cause tremendous 
variations in timing. This effect was observed occa- 
sionally in standard specified solutions also. 



Figure 4. Effect of copper chloride content on firing 
time in solutions containing 30 per cent diethylene- 
triamine. 


9.4.5 Addition of Foreign Substances 

There was reason to think that the presence of 
hydrochloric acid was beneficial to the performance 
of the SRA. Full study, however, showed that this 
was not the case. 22 It was found that generally acid- 
ity had little effect on the variance, but did tend to 
increase the mean time. As a result, recommenda- 
tions were given to the Services on the pH allowable 
for each color solution. These were incorporated in 
the manufacturing specifications as follows: Black, 
2.0 to 2.5; Red, 1.0 to 2.0; White, 1.0 to 2.0; Green, 
0.5 to 1.0; Yellow, 0.5 to 1.0; Blue, 0.7 to 1.7. 

As already mentioned, White solutions, because of 
their colorless character, required staining by the 
addition of a trace of an organic dye, Scarlet Moo. 2 


With the object of improving the temperature co- 
efficient, experiments, designed to form copper com- 
plex ions, were performed with solutions varied by 
the addition of ferric chloride, sodium chloride, and 
magnesium chloride. The results did not warrant 
further investigation, 2 nor was the presence of a com- 
pound lowering the surface tension effective. 

9.4.6 New Solutions 20 21 

One entirely new solution providing a 33^-day de- 
lay has been mentioned. Other new solutions in which 
glycerol was replaced by raffinose, and copper chlo- 
ride was replaced by ferric chloride, stannic chloride, 
or mercuric chloride were also unproductive, depend- 
ing apparently upon the age of the solution and the 
area of the tension wire exposed. Two-phase systems 
were likewise unsuitable although British workers at 
Oxford were successful in devising one which had a 
remarkably low temperature coefficient. 55 More sig- 
nificant was the development of improved compo- 
sitions involving only the original materials: copper 
chloride, water, and glycerol. Sufficient data were 
obtained to establish tables relating time to percent- 
age of glycerol, and time to specific gravity for vari- 
ous copper chloride concentrations. From these, 
isochronic lines were drawn on charts relating copper 
chloride to percentage of glycerol, and copper chlo- 
ride to specific gravity. From these plots, it was pos- 
sible to obtain the composition and specific gravity of 
solutions having the least glycerol or copper chloride 
coefficient for any mean time in the range of a given 
color. A selection of the best composition of the three 
components was thereby possible and an ampule so- 
lution, showing optimum independence of temper- 
ature, 24 was provided. 

From these charts, it was deduced that the speci- 
fied compositions of Green and Yellow solutions were 
not at the optimum position, and revised composi- 
tions (see Table 1), having lower glycerol coefficients, 
■were recommended. 25 The compositions for White 
and Blue solutions appeared to be, at least, satisfac- 
tory. Unfortunately, the recommendation was never 
put into practice because of its lateness. Should a 
production of the Mark I Pencil be undertaken in the 
future, other specifications for Yellow and Green so- 
lutions appear desirable. 

9.5 WICKS 

The action of the wick in the ampule chamber was 
to insure a constant supply of fresh corroding solu- 




SPRINGS 


61 


tion to the iron wire. Obviously, bad wicking would 
result in high deviation in time. The manufacturer’s 
practice of using hand-formed pellets of cotton was 
demonstrated to be responsible for a certain amount 
of variation. 12 A study was undertaken of several 
fibers possible for the purpose, including surgical 
cotton, Kotex, fiberite. No great improvement over 
the use of chemically neutral cotton could be shown. 
However, it was found that preformed dental pellets 
of fairly uniform weight (14 milligrams) gave uni- 
form performance and were considerably easier to 
use in the assembly line. 36 40 Incorporation of this 
minor change in the specifications would seem desir- 
able. 

9.6 REACTION CHAMBER 

9.6.1 Sealing 

The SRA-3 reaction chamber consisted of a thin 
crushable copper cylinder, a center plug of copper- 
plated brass, and a similar end plug. While not water- 
proof, the chamber was necessarily constructed to 
prevent leakage of the ampule solution after crush- 
ing. Sealing of the chamber was provided at the cen- 
ter plug by the use of Plasticine or molding clay, 
which was injected around the tension wire at the 
point where it passed through the center plug. Sealing 
at the end plug was obtained by passage of the ten- 
sion wire through a very small hole, and firm pressure 
under a lead washer surrounding the anchoring screw 
on which the tension wire was wound. While the 
suitability of Plasticine and similar materials was 
demonstrated, 36 there was more question about the 
lead washer, which on occasion lubricated the tension 
wire allowing it to slip on long standing. 2 A recom- 
mendation that soldering be substituted for the screw 
procedure of anchoring was not acceptable to the 
manufacturers. 

In the case of the volatile solutions containing 
n-propyl alcohol (see Section 9.4.4), complete clo- 
sure was obtained by dipping the Pencil end in col- 
lodion solution. This was in line with the practice fol- 
lowed by the Russians, who dipped their Pencils in a 
high melting wax such as beeswax. 5 It would appear 
that the present method of sealing the reaction cham- 
ber was sufficiently good for the use of the Pencil 
above water, and, since the device was not suitable 
for use below water for other reasons, it would appear 
to have been adequately handled. 


9.6.2 Materials 

The crushable copper tube was annealed soft and 
provided with a slight flare at either end where it 
fitted over the end or center plugs. It was found that 
the manufacturers were brightening this tube by a 
series of acid and alkaline washes with the result that 
the tube as assembled in the Pencil had a distinct 
alkaline coating which interfered notably with the 
performance of the ampule solution. 15 Tests showed 
also that the end and center plugs, which were 
brazed, required a complete and smooth coating of 
copper plate in order to give resistance to the cor- 
rosive action of the ampule solutions. It seemed that 
the zinc contained in the brass plugs, if exposed to 
the solutions, would enter preferentially into reaction 
with them, thus altering the effective concentration 
of copper chloride and unpredictably affecting the 
timings. 8 ’ 9 


9.7 SPRINGS 

The quality of springs gave trouble throughout the 
production of the SRA. Wire of a suitable resiliency 
was hard to obtain, and the specification of flat- 
ground ends was never met. This tended to throw the 
striker off center and occasionally resulted in misfires 
(see Section 9.9), but was, on the whole, not as seri- 
ous as the variation in length among springs and the 
tendency of all springs to take permanent set on 
standing. It was interesting to note that the Russian 
time Pencil spring had precision-ground ends. 5 

Manufacturing procedure at the start of American 
production called for the loading of the spring to po- 
sition, and, since it was clearly shown that springs 
varied in length by a considerable factor, it was ap- 
parent that a variation in load was being obtained, 
which was found by actual tests to lie between 14 and 
20 lb. This meant that the tension wire was under a 
variable tension, and hence wires in different Pencils 
would part at different times. A tightening up of the 
acceptance of this part served to correct this diffi- 
culty. 2 

Ultimately, a change-over from position loading to 
dead- weight loading in manufacture was achieved 
and the specification was rewritten so that the 
springs were loaded to 15 + 1 lb, giving greatly im- 
proved performance. No solution was ever obtained 
to the problem of permanent set, which by experi- 
mentation was found to result in a variation of timing 
of about 3.4 per cent per lb of load change. 2 ’ 18 > 28 > 39 


Restricted J 


62 


PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 


9.8 PRIMERS FOR SRA-3’S 

The OSS model of the Pencil utilized special prim- 
ers, which upon request the division undertook to 
test to determine their behavior on prolonged im- 
mersion, accelerated aging, and exposure to condi- 
tions of high humidity and temperature. An unpre- 
dictable failure of approximately 0 to 2 per cent of 
the primers was obtained, and higher percentages on 
prolonged immersion. Very good stability to acceler- 
ated aging was noted. 38 In the SRA-3 the primer was 
crimped in tothe end of the Pencil flush with a steel 
spring snout which was of a size to receive Primacord 
or Bickford safety fuze. This feature was lacking in 
the Corps of Engineers firing device delay type Ml, 
and no tests were performed by the division on the 
initiating system of that fuze. 

9.9 PLUNGER 

As already mentioned, the use of unground springs 
gave an eccentricity to the travel of the plunger 
which at first was not felt to be serious. The point 
was, however, investigated, and it was found 44 - 45 
that the primer caps in the SRA-3 had varying sensi- 
tivity, depending upon the location of the blow. 
With eccentric initiation, increasing failure could be 
expected as the primer struck further off center. 
Correction of this difficulty was easily achieved by a 
redesign of the plunger, which in the SRA had been 
made from brass rod by screw machine processes but 
which in the SR was made from square bar brass at 
slightly increased cost. The latter design allowed the 
plunger to rest on the walls of the brass striker tube 
which guided it to the primer insuring a central 
strike. A change in the SRA specifications completely 
corrected the difficulty. 

The energy with which the primer was struck by 
the plunger was the function of the spring, as well as 
the friction encountered by the plunger in traveling 
through the brass tube. The energy imparted (67 oz- 
in.) to the striker by a spring at 15 ± 1 lb load was 
more than sufficient to give 100 per cent functioning 
with central or intermediate eccentric strike on the 
primer but to fail on extremely eccentric strike (re- 
quiring 111 oz-in.). 

9.10 PACKAGING 

Mention has already been made of the suscepti- 
bility of Pencils made with tinned wire to storage 
under conditions of high humidity. The numerous 


pinholes in the tin surface provided excellent oppor- 
tunity for corrosion and weakening of the tension 
wire with the result that after two years of exposure 
fully 50 per cent of the stored Pencils would be found 
to have fired. Those which had not fired were obvi- 
ously in a weakened condition and, hence, a danger. 
The problem of protecting the Pencil from this cor- 
rosion effect was a serious one which would have been 
met by the adoption of electrogalvanizing. Unfortu- 
nately, failure to accomplish this meant that another 
solution had to be forthcoming. This was obtained in 
the use of a packaging envelope for each individual 
Pencil. 

The last considerable fraction of the OSS produc- 
tion was packaged in transparent tubes of polyvinyl 
chloride [PVC]. The very remarkable improvement 
in functional efficiency thereby obtained was clearly 
demonstrated in elaborate tropical weathering cycles. 
Strangely enough, unpacked Pencils behaved with 
equal efficiency. It was only when Pencils were pack- 
aged in tins that the severe loss of storage resulted. 
The explanation of this lay in the retention within 
the tin of ambient humidity and favoring of corro- 
sion. In future production the packaging of Pencils 
individually in PVC or similar impervious containers 
would seem warranted. 49 * 54 

9.11 TEST PROCEDURE 

9.11.1 For Research 

For several years the Division, through two major 
contracts, did a large amount of work on testing and 
improving the time Pencil. This work was correlated 
to some degree with similar activities in Britain and 
with test procedures in force at the Engineer Board 
at Fort Belvoir, Virginia. At the start, there was no 
agreement among these various groups, which were 
widely scattered geographically, as to the manner of 
conducting time tests or the manner of analyzing the 
results obtained. This lamentable situation was cor- 
rected 57 by the adoption of a set of conditions for 
tests and agreement on the statistical handling of the 
data. For the former, several temperatures were se- 
lected and thermostatic chambers provided so that 
the temperature variable could be controlled. In ad- 
dition, agreement was achieved on the position which 
the Pencil should occupy while under test. This was 
accepted as horizontal, because it appeared to be the 
most logical position for field use. It was agreed that 


TEST PROCEDURE 


63 


in the horizontal position the Pencil should be 
mounted so that the tension wire which is unsym- 
metrically placed in the reaction chamber should be 
down. Crushing was accomplished in the horizontal 
plane by the use of especially designed pliers having 
jaws of a given area and stroke to provide entirely 
uniform crushing. No figures obtained from less than 
50 test results were considered as entirely suitable for 
proof of any recommendation. 

Figure 5 11 is a sample of the presentation of such 
data in graphical form for a batch of 26 Yellow Pen- 
cils at 25 C. The number firing in any given time in- 
terval of 20 min is recorded. By the mode is meant 
that point in time at which the greatest number of 
Pencils fired; by the median is meant that point in 
time midway between the two extremes of the whole 
group; and by the mean is meant the arithmetic 
mean of all the timings. 

Presentation of the data obtained was done both in 
tabular and graphical form, according to conventions 
adopted by the research groups. 57 

In Figure 6 is shown a rack with 10 Pencils of 
which half have been crushed and are ready for in- 
sertion into the thermostatically controlled chamber. 

The importance of this procedure for handling re- 
search on time delays cannot be over-estimated. It 
was not until this procedure had been adopted that 
the maze of complexity of the Mark I Pencil could be 
penetrated. Should any further research be done, it is 
recommended that it be undertaken with the same or 
similar definitions and prescribed procedures. 

Having set down the rules by which research would 
be conducted, it was interesting and profitable to 
learn how changes in these rules would affect opera- 
tion of the Pencil. A study was therefore undertaken 
of the effect of orientation and method of crushing on 
timings obtained. This had, in addition, important 
field use, since, if some simple relationship could be 
found, the field could be instructed in the optimum 
usage of the Pencil. Considerable variations were 
found depending on whether the wire was up or down 
during the operation of the delay, on the direction in 
which the crushing took place, and on the extent of 
crushing, as well as on the plane in which the Pencil 
rested while operating. 41 - 50 

It appeared as a generalization that Pencils com- 
monly used in pairs and activated in the field led to 
timings of about 25 per cent shorter than those ob- 
tained under accepted testing conditions, with the 
shortest mean timings being obtained when the Pen- 
cil made an angle of 45 degrees with the horizontal. 



TIME IN MINUTES 

Figure 5. Sample timing chart of Yellow Mark I 
Pencil. 

The extreme mean and maximum timings were ob- 
tained when the Pencil was tested vertically with the 
snout down. This most unfavorable of all positions 
was also the one least likely to be used in the field 
and, hence, was not considered serious. In fact, in 
any given operation, the variable method of crushing 
and placing of the time delay made exact prediction 
of the time at which the Pencil would operate a 
highly problematical matter. Nevertheless, the gen- 
eral value of tables, such as that given in Section 9.12, 
is not discredited. 


64 


PENCIL (SRA-3) FIRING DEVICE, DELAY TYPE, M-l 





Figure 6. Timing rack for Mark I Pencil. 


9.11.2 For Quality Control in 
Production 32 - 42 > 47 

Although production and quality control of it were 
not the function of Division 19, advice was given 
which ultimately assisted in a satisfactory method of 
batch analysis and which was capable of detecting 
trends in quality of the assembly lines prior to the 
point at which production would have been rejected. 
This necessitated a rigorous inspection procedure of 
production as it emerged from the factory, and it is 
to the credit of OSS that they and their British liaison 
officers insisted upon and obtained adequate testing 


facilities and personnel by which all production under 
their auspices met a very high standard of perform- 
ance. The references noted contain the details of this 
system, which worked so well. 

A complete analysis of American Pencil production 
for nearly one year 56 is interesting in this regard. 
From it, data may be quoted which indicate the 
parts of the Pencil against which the percentage of 
variance may be assigned. It appeared that the ulti- 
mate, which could be expected by the Mark I by 
careful quality control, was about 12 to 16 per cent 
for any individual sample, and the percentage of vari- 
ance caused by wire variations averaged around 15.4, 


Table 4. Chart of operational timings of SRA-3’s. 51 


fC 

tF 

Black 

OM ST 

Red 

OM ST 

White 

OM ST 

Green 

OM ST 

Yellow 

OM ST 

Blue 

OM ST 

- 32 

-25 


.... 



3 day 

1.3 day 







- 18 

0 

.... 

.... 

45 min 

20 min 

17.5 hr 

8 hr 

2.2 day 

1.0 day 

8.5 day 

3.8 day 

23 day 10 day 

— 4 

-f- 25 

36 min 

16 min 

25 min 

11 min 

5.5 hr 

2.5 hr 

19 hr 

8.5 hr 

2.0 day 

20 hir 

5.0 day 2.2 dav 

+ 10 

50 

15 min 

7 min 

17 min 

8 min 

2 hr 

55 min 

6.5 hr 

3.0 hr 

14 hr 

6.0 hr 

1.3 day 

14 hir 

24 

75 

9 min 

4 min 

15 min 

7 min 

1 hr 

27 min 

2.7 hr 

70 min 

5.5 hr 

2.5 hr 

11.5 hr 

5 hr 

38 

100 

5 min 

2.0 min 

8 min 

3.5 min 

32 min 

14 min 

72 min 

30 min 

2.5 hr 

65 min 

5.2 hr 

2.3 hr 

52 

125 

4 min 

1.5 min 

5 min 

2 min 

20 min 

9 min 

40 min 

18 min 

80 min 

36 min 

2.5 hr 

1.1 hr 

66 

150 

3 min 

1 min 

4 min 

1.5 min 

15 min 

6 min 

25 min 

10 min 

46 min 

21 min 

80 min 

36 min 


OM When two Pencils are used in the same charge, the OM is the most likely timing. When only a single Pencil is used, the value should be 
increased by about 15%. 

ST The ST is a reasonably safe time. Timings shorter than the ST should not occur more often than once in a thousand trials. 



PERFORMANCE 


65 


and for ampule variations averaged 16.2. By per- 
centage of variance was meant the quantity a' 

x 

where 

(ZX) 2 _ (ZX) 2 1» 

(n — 1) n(n — 1)J 

and where X is the observed timing, x is the deviation 
from the mean, and n is the number of Pencils firing. 

9.12 PERFORMANCE 46 48 51 

The data given in Table 4 were obtained from 
many hundred tests according to the rigorous pro- 
cedures indicated in Section 9.11 ; since all operations 
were conducted using two Pencils, the columns 
headed OM are most significant. In all cases it should 
be remembered that the personal idiosyncracy of the 
user in placing and operating the Pencil in the field 
may be expected to alter the timings by a factor of as 
much as 25 per cent. Whether this is serious or not 
will depend upon an individual operation. In general 
the condition would be serious only in the short tim- 
ings, where because of some freak of accumulated 
effects a functioning in considerably less than the 
specified period might endanger the user. The figures 
given in columns headed ST are not of great value, 
except as indicating the extent of risk which an oper- 
ator would encounter in using Pencils. This risk is 
probably not significant under wartime conditions. 



The same data, presented in a more forceful form, 
is found in Figure 7 which shows the relationship be- 
tween time and temperature for all colors. 


Chapter 10 

MARK II PENCIL 


10.1 INTRODUCTION 9 10 

The performance of the Mark I Pencil (see Table 4 
in Chapter 9) made it abundantly clear that the 
greatest refinements in production technique would 
never provide a delay, which in the field would give 
essentially constant timing for expected temperature 
changes. Progress could be made in producing delays 
having less variability and greater reproducibility, 
but, because the Mark I was based chiefly on a chem- 
ical reaction, it would always be subject to wide vari- 
ations in timings caused by moderate variations in 
temperature. This is well illustrated by the figures 
for White delays, which at 0 F required 17J^ hr for 
operation and at 125 F took only 20 min. There was 
therefore an operational requirement for a time delay 
having the dimensions and essential operation of the 
Mark I Pencil but being independent of temperature. 
This was a realistic approach, for the man in the field 
could hardly be expected to tell within 5 or 10 de- 
grees what the ambient temperature was and to ap- 
ply the table of temperature corrections listed for the 
Mark I. 

It appeared that the problem might be readily 
solved by substituting, for the chemical action of the 
Mark I, an electrochemical reaction in which the 
iron tension wire of the Pencil would be one of elec- 
trodes of a galvanic cell. The other electrode in this 
design would consist of a silver wire coated with fused 
silver chloride. The following reaction would there- 
upon be set up when electrolyte was added to the 
system: 3^Fe + AgCl = HFeCh + Ag. This spon- 
taneous reaction would take place with resulting dis- 
appearance of the iron wire at a rate which would de- 
pend upon the value of a resistor connecting the iron 
and silver poles of the cell. The maximum time would 
be obtained on an open circuit with no connecting 
resistor and the least time when a short was provided 
between the two electrodes. Experience soon indi- 
cated that a maximum timing range varying between 
17 hr and 10 min could thereby be obtained. Since 
this range was also the range of the Mark I Pencil, 
the system appeared suitable for use in the develop- 
ment of an improved device. 

Being electrochemical in nature rather than chem- 
ical, such a device would be independent of temper- 
ature, and variation in timing would be obtained, not 
by changes in electrolyte or electrodes, but solely by 


variation of the external resistance. The simplicity 
with which this design lent itself to the basic Mark I 
features is apparent in Figure 1 *!. 

10.2 DESCRIPTION AND OPERATION 1 10 

Reference to Figure 1 will show that many parts of 
the Mark I design were retained and that others were 
only slightly altered to accomplish the change of the 
Mark I from a chemical to an electrochemical device. 
The overall dimensions remained constant, with the 
exception of the end cap, which in the Mark II was 
slightly larger in diameter than the rest of the Pencil. 
Its operation was identical with that of the Mark I, 
in that the user crushed a soft copper tube within 
which was contained a glass ampule filled with the 
electrolytic solution. Unlike the Mark I, crushing 
was preferably performed with the snout end of the 
Pencil upward so that the released electrolyte might 
flow to the cell end of the device and there be soaked 
up by the cotton wick. This will be further discussed 
in Section 10.4.4. Following crushing, the safety strip 
would be removed and the Pencil placed in any de- 
sired position. Its operation from there on was en- 
tirely mechanical and analagous to the Mark I. 

The steel tension wire was subjected to galvanic 
action over that portion covered by the cotton pack- 
ing in the bakelite end cell. Upon the release of the 
electrolytic solution, which was either a solution of 
ammonium chloride or calcium chloride, the above- 
mentioned chemical reaction began, with the result 
that the iron wire was eroded and the silver chloride 
electrode reduced. This electrode and the iron wire 
both passed through the base of the bakelite cell 
head, were firmly crimped to prevent slippage, and 
were connected by soldering through a length of 
standard nichrome, or similar resistance wire, which 
for convenience was wound on a bobbin cut into the 
side of the bakelite cell. 

10.3 CHANGES FROM THE MARK I 
DESIGN 

10.3.1 Wire 2 4 

Taking advantage of the discoveries in Mark I re- 
search, electrogalvanized steel wire was employed 
in preference to tinned music wire and a change was 


66 


CHANGES FROM THE MARK I DESIGN 


67 





Figure 1 . Cut-away model, assembled model, exploded model — Mark II Pencil. 


made from 20-mil to 10-mil wire to meet the normal 
timing range of the Mark I colors. Protection of this 
wire, which was low (0.60 per cent) in carbon, was 
accomplished by electrogalvanizing to a coating 
thickness of 1 X 10 4 in. + 25 per cent. The wire was 
anchored, both at the cell end and at the striker end, 
by a new method of attachment. This was necessi- 
tated because the set screw used in the SRA-3 could 
not be employed in the Mark II on account of the 


limited space at the end plug. Anchoring was ob- 
tained when a small strip of fine, hard-temper copper 
tube was slipped over the galvanized wire and 
crimped in a double V by a special tool. Numerous 
tests showed that this method of attachment was 
firm and that the wire would invariably break before 
the V-crimp would loosen. It was, of course, essential 
that, on crushing the copper tube, the iron wire 
should not make contact with the copper to provide 





68 


MARK II PENCIL 


a short. This could be corrected either by lining the 
copper tube of the reaction chamber with an insulat- 
ing material or by covering the iron tension wire with 
a sheath of similar material. The former procedure 
was found definitely preferable. 


10.3.2 Solution 2 - 3 - 4 

It was shown that, as the volume of the solution 
was increased beyond a certain value, the mean time 
tended to increase and the precision of timing to de- 
crease. As the volume was decreased, the reverse took 
place and duds appeared. Fortunately between the 
range 0.20 and 0.25 cc the curve of the mean time 
versus the volume of solution became almost flat and 
the precision of time attained a maximum. Hence the 
volume of the solution was fixed at 0.23 ± 0.01 cc. 

It was originally intended to use ammonium chlo- 
ride as the electrolyte for all the Pencil colors. How- 
ever, it was soon found that in the longer delays 
(White through Blue), the time of operation of the 
delay was sufficient for a slow, secondary reaction to 
take place involving iron and ammonium chloride. 
Calcium chloride solution did not give this slow 
spontaneous corrosion of the steel wire, and hence 
was desirable for the longer timings. In the lower 
timing ranges, however, calcium chloride solutions 
were appreciably inferior to ammonium chloride with 
respect to temperature coefficient. Hence two solu- 
tions were eventually used for the whole range of the 
Mark II Pencil: a solution containing 17 per cent 
ammonium chloride for Black and Red Pencils, and 
a solution containing 20 per cent calcium chloride for 
the other colors. To these solutions was added 5 per 
cent by volume of w-propanol, which functioned as a 
wetting agent and increased the speed with which the 
wick could soak up the released electrolyte. 

The use of the same solution for all Pencils would 
have simplified manufacturing and would have elim- 
inated any possibility of incorrect ampule assembly. 
If this were sufficiently important, calcium chloride 
would be preferred, but in that case the Black Pencil 
would have a mean time of 12 min instead of the 
specified 10. It should be evident that the change 
from copper chloride glycerin solutions to those con- 
sisting only of ammonium or calcium chloride and 
propyl alcohol simplified production. Moreover, the 
concentration of the solutions was easy to control and 
the functioning of the Mark II Pencil was not sensi- 
tive to even gross variations. 


10.3.3 Ampules 6 

Since the Mark I Pencil in its final form required 
an ampule containing 0.7 cc of solution, the change in 
the Mark II necessitated the production in quantity 
of a very much smaller ampule. This caused some 
difficulty, especially in the sealing operation where 
the presence of the propyl alcohol was objectionable 
and where calcium chloride tended to wet the glass 
and to spoil the seal. However, with the assistance of 
several manufacturers, th<* problems connected with 
the new ampule were overcome and test procedures 
were set up which eliminated weak ampules. An en- 
tirely satisfactory ampule production was achieved, 
and properly made ampules were found to withstand 
heating to 180 F and to be resistent to moderately 
rough handling. 

10.3.4 End Plug 

The brass end plug of the Mark I design was re- 
placed by a bakelite cell unit bearing, as already men- 
tioned, the silver-silver chloride electrode and pro- 
vided with a small hole through which passed the 
iron tension wire to be crimped and soldered at the 
back of the plug. Manufacture of the bakelite cell was 
not a difficult screw machine problem. The chief 
difficulty with the part occurred in producing the 
silver-silver chloride electrode and in inserting the 
cotton wick. A spoon-shaped electrode, formed from 
wire and coated with molten silver chloride by ma- 
chine dipping, gave good performance. The theoreti- 
cal amount of silver chloride needed was about 20 mg 
and the production electrodes were provided on the 
average with twice that quantity. 


10.3.5 Wicks 3 - 6 

Absorbent cotton pellets were used to stuff the 
bakelite cell and to bring the electrolyte into intimate 
contact with the electrodes. It was found that the 
weight of these pellets influenced the mean time and 
the precision of timing with the optimum weight ly- 
ing between 35 and 40 mg. Preformed dental rolls of 
the right weight and dimensions were obtained for 
the semi-production and would presumably represent 
no problem to a future producer of the device. They 
would be essential, since only by their use could as- 
surance be given that each Pencil had received ex- 
actly the correct weight of wicking. 


PERFORMANCE 


69 


10.3.6 Copper Tube 2 3 4 6 

Because the length of the SRA-3 was maintained 
while the end plug length had been considerably in- 
creased, the crushable copper tube comprising the 
reaction chamber had suffered in overall length. The 
effect of this was to make it stiffer to crushing when 
located in an assembled Pencil. To match the easy 
crushing properties of the SRA-3, another tube had 
to be employed. Fully annealed tubing was used, and 
the wall thickness (0.11 in.) was adjusted to give this 
appropriate stiffness. It was coated to provide insula- 
tion of the reaction cell, by dipping in Roxalin Flex- 
ible Lacquer No. 3181. 

10.3.7 Center Plug 6 

In the semi-production of the Mark II which was 
undertaken by the division, the center plug of the 
Pencil was identical with that used in the Mark I, 
except that the Plasticine sealing compound was 
omitted. Subsequent tests indicated that this was a 
mistake, and in any future production sealing of the 
reaction chamber from atmospheric corrosion by the 
use of Plasticine should be retained. 

10.3.8 Spring 5 

With a change in the diameter of the tension wire 
and a drop in its breaking load from the Mark I value 
of 35 lb to the Mark II value of 29 lb, a correspond- 
ing reduction was required in the weight loading of 
the spring. It was impossible to use the same spring 
employed in the SRA-3, since full loading to 15 lb 
was required to reduce the length sufficiently so that 
the striker would clear the inspection port. A new 
spring was therefore specified for the Mark II, and it 
was determined that it could be safely loaded to 
10 % lb without fatigue and still deliver a force suf- 
ficient to fire the primer caps of the standard SRA-3 
reliably. 

10.4 PERFORMANCE 7 8 

10.4.1 Temperature Coefficient 

The great virtue of the Mark II Pencil was the in- 
dependence of its timing to temperature change, as 
shown by exhaustive tests conducted at the central 
laboratory of the division and by the developing con- 
tractor. Figure 2 gives the values obtained by these 
extensive tests and shows, more clearly than words, 
the remarkable performance which the Mark II pos- 


sessed. The same figure bears the corresponding 
curves for the SRA-3 and the improvement is note- 
worthy. The letters refer to the colors. 



Figure 2. Time-temperature chart — Mark I and 
Mark II Pencils. 


10.4.2 Per Cent Deviation 

It was interesting to learn that, although not an- 
ticipated, the percentage deviation of the Mark II 
Pencil was in general equal to or lower than that ob- 
tained with the Mark I (see Section 9.11.2). In Fig- 
ure 3 are plotted the values of this function for the 
different colors. 

10.4.3 Tropical Weathering 8 

The resistance of the Mark II Pencil to prolonged 
storage was determined and compared with the per- 
formance already obtained with the Mark I, which, 
it will be recalled, required individual packaging in 
polyvinyl chloride tubes to insure arrival of the de- 
vice in a usable condition in the field. After tests at 
the division’s central laboratory, it appeared that the 
Mark II Pencil was somewhat more sensitive to pro- 
longed exposure to high humidity and high tempera- 
ture than the Mark I. This feature was, however, not 
of a different order of magnitude and presumably the 
Mark II Pencil if properly protected in the recom- 
mended manner would give no difficulty in the field. 


70 


MARK II PENCIL 



0 50 100 150 0 50 100 150 

TEMPERATURE - F 
O—O MKH (MRL DATA) 
x x MKD ( L 8 N DATA) 

MK I (MRL DATA) 

AS A FUNCTION OF TEMPERATURE 

Figure 3. Reproducibility of Mark I and Mark II 
Pencils. 

10.4.4 Positional Operation 8> 9 

Throughout the development of the Mark II Pen- 
cil, the interested liaison officers in OSS and the Corps 
of Engineers were acquainted with the fact that, for 
optimum performance, the Mark II Pencil required 
initiation with the cell end down, so that the crushed 
ampule could deliver its contents to the wick. By 
numerous tests it was shown that even this require- 
ment was not critical and that crushing could be con- 


ducted in almost any position except with the snout 
end down and, if followed by a whipping or tapping 
action, would give reliable performance. From a tech- 
nical point of view it did not appear that this added 
requirement in the use of the device would be a seri- 
ous limitation. 

Such turned out to be the case, however, when field 
appraisal was obtained using the NDRC semi-pro- 
duction models. 9 It appeared that those in charge of 
training users of such delays did not care to grapple 
with the additional requirement of positional activa- 
tion, even though admitting that the Mark II Pencil, 
by its superior temperature performance, had given 
a delay of much greater value for special field use 
than the original Mark I Pencil. Whether a redesign 
of the Mark II Pencil could be undertaken which 
would provide for this deficiency is a matter of ques- 
tion. Unfortunately the development reached com- 
pletion too late in the war for the division to have 
undertaken the study. 

It was believed, and is still the opinion of the 
writer, that the advantages of the Mark II more than 
outweighed this mild inconvenience in its use. It is 
believed that this can be shown in no more convinc- 
ing way than by Table 1 in which the temperature 
coefficients of the SRA-3 and the Mark II Pencil are 
compared. 

Table 1 . Comparison of temperature coefficients of 

SRA-3 and Mark II Pencil. 

Ratio of mean timing at 10 F to 150 F 

Color SRA-3’s Mark II Pencils 


Black 

46 

3.4 

Red 

11 

1.9 

White 

47 

1.7 

Green 

104 

1.7 

Yellow 

133 

1.6 

Blue 

248 

1.8 


Chapter 11 

INCENDIARY PENCIL (SRI) 


11.1 INTRODUCTION 

Both the Mark I and the Mark II Pencils, dis- 
cussed in Chapters 9 and 10, were designed for the 
activation of explosive devices or charges. They could 
equally well serve the purpose of initiating incendiary 
charges, and this chapter describes how that was 
achieved. 

Two methods were employed, in both cases de- 
pending upon the development of a Matchhead 
which would be activated by the mechanical opera- 
tion of the time Pencil. In the first case, the primer 
and spring snout ending of the SRA-3 were replaced 
by the Matchhead ending, which was crimped into 
the brass striker tube of the Pencil. In the second 
case, the SRA-3 was used as it stood and the Match- 
head was simply inserted into the spring snout in 
juxtaposition to the primer cap. The former type of 
use was silent, but the latter made the usual noise of 
the exploding primer. In certain operations this fea- 
ture would not be serious, in others silence might be 
a requirement; hence, the probable need for both 
types of usage of the Matchhead in field operations. 
Needless to say, the second type recommended itself 
particularly, in that no alteration in the standard 
SRA-3 was required for conversion to the Incendiary 
Time Pencil. 

11.2 DETAILS OF CONSTRUCTION 

’ n.2.1 Magnesium Matchhead 1 

In its final form the most satisfactory Matchhead 
developed consisted of a magnesium cell made by 
reaming out a rod of magnesium. It had an overall 
length of % an outside diameter of 0.278 in., 
and an inside diameter of 0.218 in. Nearly two- thirds 
of this cavity was filled with a hot burning composi- 
tion known as BA-29- A as follows: barium peroxide 
anhydrous, 75 + 3 percent; potassium perchlorate, 
3 ± 34 per cent; red iron oxide, 934 ± 1 P er cent; 
magnesium powder Grade A coated with 3 per cent 
linseed oil dried 24 hours, 1234 per cent; paraffin oil, 
34 per cent. This material was pressed by hand into 
the magnesium case and was followed by a small 
volume of SM composition having the following spec- 
ifications: potassium chlorate 47 + 2 per cent; mag- 
nesium powder Grade B coated with 3 per cent linseed 


oil dried for 24 hours, 10+1 per cent; hard wood 
flour, 6+1 per cent; infusorial earth, 5 + 1 per 
cent; red iron oxide, 10 + 1 per cent; powdered glass, 
1234 ± 1 per cent; J4 second nitrocellulose in 60 per 
cent ethyl acetate and 40 per cent butyl acetate, 
934 + 1 per cent. The last ingredient of this compo- 
sition made it sufficiently moist to be plastic, and, 
while in this state, there was inserted into it the head 
of a Strike- Any where match. This was squeezed 
down to a distance of 0.020 + 0.010 in. from the end 
of the magnesium body. The unit as assembled was 
then dried at room temperature for 40 hr, inspected 
for uniformity, and sealed against moisture by a drop 
of molten Lukon wax compound heated to 300 F. 
After inspection, the Magnesium Matchheads were 
pickled in a standard acid solution to give them re- 
sistance to corrosion. 

When assembled, by crimping into the standard 
Pencil, a modified Pencil known as the signal relay 
incendiary (SRI) resulted. This required a slight 
modification in the striker of the SRA-3. In contrast 
to the shape required for firing a primer cap, the In- 
cendiary Matchhead required a sharp-pointed needle. 
Figure 1 illustrates this, as well as the assembled de- 
vice. The point of this striker formed an angle of 
45 degrees and was roughened by a Parkerizing tech- 
nique. The body of the striker, as seen in the illustra- 
tion, was provided with several vent holes to prevent 
explosions from the large volume of gas liberated by 
the quick-burning compositions. 

Operation of the Pencil in the usual manner gave 
essentially silent initiation of the Matchhead when 
the striker point penetrated the wax coating and 
pierced the underlying safety Matchhead surrounded 
by the quick-burning compositions. These in turn 
ignited the magnesium casing, which burst into 
flame. If the Matchhead were to be used by the 
second technique outlined in Section 11.1, the user 
would first be required to remove the protecting wax 
overcoat so that the flame from the primer cap could 
each the embedded safety Matchhead and initiater 
it. This usage is illustrated in Figure 2. 

11 . 2.2 Celluloid Matchhead 4 - 8 

A preliminary design, differing from the one de- 
scribed immediately above, chiefly in the fact that 

71 




72 


INCENDIARY PENCIL (SRI) 









Figure 1 . SRI-Mg: assembled and exploded views. 


the case was celluloid rather than magnesium, was 
also developed. However, considerable difficulty was 
encountered in making the Celluloid Matchhead im- 
pervious to water vapor because celluloid passes 
moisture. Attempts to give this Matchhead protec- 
tion under adverse storage conditions occupied test- 
ing laboratories for many months, and eventually 
some success was attained by the use of a thin, trans- 
parent celluloid window in place of the sealing wax 
mentioned in the Magnesium Matchhead. Further 
improvement resulted on dipping in thermoplastic 
wax Dewey and Almy No. TP317. 

Crimping of this type of head into the SRA-3 
sometimes caused minute fissures to appear in the 
protecting surface and, under very prolonged storage 
at high humidity and high temperature, failure of the 
device frequently occurred because of the penetra- 
tion of water vapor to the water-sensitive filling. 
This prompted the change to the magnesium case, 
which was recommended by the division as the final 
solution to the problem. Unfortunately, production 
of the Celluloid Matchhead was many times larger 
than the Magnesium Matchhead because of its 
earlier development. 




I 

I 


I 


fi 



Figure 2. The method of using a separate magnesium 
igniter in a standard SRA. From left to right: The 
SRI-Mg; SRA and magnesium igniter; SRA and mag- 
nesium igniter with wax covering of Matchhead re- 
moved; magnesium igniter inserted in spring snout of 
SRA. 


11.3 PERFORMANCE 7 

n.3.1 Resistance to Weathering 2 

Exposure of SRFs to extremely severe cycling con- 
ditions indicated that in the case of the magnesium 


head, reliable performance could be guaranteed for 
several times any period obtainable with a standard 
time delay Pencil. The Matchheads would not, how- 
ever, withstand indefinite treatment of this severity 
any more than would the unpackaged SRA-3’s. The 
recommendation was made therefore that the SRI’s 



PERFORMANCE 


73 


be packaged in watertight containers, similar to 
those which had already been shown necessary for 
the SRA’s (see Section 9.10). This guaranteed the 
arrival of the SRI in the field in a perfect condition 
and assured its satisfactory performance. 


11.3.2 Use as an Incendiary 5 

The SRI in itself proved to be a simple, reliable, 
and extremely small incendiary device for the igni- 
tion of targets having a fair combustibility. Numer- 
ous tests on a number of wooden structures showed 
that placement of an SRI between two vertical 
wooden surfaces 1 in. apart would give reliable ig- 
nition, provided the water content of the wood did 
not exceed 15 per cent. This figure was reasonable for 
most wood stored indoors or in hot, dry countries. 
For ignition of more difficult targets an auxiliary in- 
cendiary material would have to be provided. 

It was found also that the efficiency of an SRI 
could be considerably increased by the use of it in 
conjunction with several additional Magnesium 
Matchheads; Figure 3 illustrates this application. 

With multiple heads arranged in this manner, 
there was a delay of 6 to 10 sec between the ignition 
of the successive heads, which were arranged so that 
the waxed end was flush with the solid magnesium 
end of the next head. This arrangement was required, 
for, if the igniter heads were joined so that the mag- 


-r 


nesium was heated before the Matchhead was lit, 
there was a considerable probability of detonating 
the igniter mix. By such a simple procedure as illus- 
trated in Figure 3, the effectiveness of a single SRI 
could be more than tripled. 


11.3.3 Use as an Igniting Fuze 3 6 

The first value of the SRI was in combination with 
incendiary devices having a large charge of fuel, and 
its use there was very general. It could be counted 
upon to ignite thermite through the use of a first fire 
mixture, jellied petroleum munitions, and has al- 
ready been specifically mentioned in Chapter 2, 
where it was used with the Paul Revere to ignite a 
magnesium “goop.” 

Indeed, wherever a delayed action incendiary of 
great potency was needed, the SRI could be recom- 
mended. This could be done either directly by pick- 
up of the fire from the burning Matchhead or indi- 
rectly by the use of safety fuze, for it was found 6 
that the SRI was well adapted to silent, time delay 
ignition of safety fuzes. If one end of the fuze were 
split with a sharp knife for a distance of about 1 in. 
and the cut faces taped onto the magnesium head of 
the SRI, the safety fuze was reliably ignited. In this 
way silent ignition with further delay could be used 
in those cases where safety fuze was required for 
operational reasons. 3 





Figure 3. SRI-Mg with triple head: assembled device and separated parts. 


Chapter 12 

CLOCKWORK TIME DELAY (DEMOLITION FIRING DEVICE MARK 3 ) 

12 -1 INTRODUCTION 3. The device was as compact as possible, measur- 


There are occasions in demolition operations when 
it is desirable to have a time delay fuze of greater ac- 
curacy and of longer delay timing than can be pro- 
vided by such chemical and electrochemical systems 
as have been described in Chapters 9 and 10. These 
operations may be either under water or above. A 
general requirement would therefore seem to exist for 
a small waterproof, cheap, and accurate delay. Such 
requirements can in practice be met most practicably 
by a fuze based upon an inexpensive clockwork. No 
originality is claimed for this idea, however, it would 
seem that the American Services lacked a device of 
the general characteristics described. This was in 
spite of the fact that practically every other Army in 
the world was well equipped along these lines. The 
Germans in World War II made frequent use of 
clockwork delay fuzes, of which they had an abun- 
dance of types and models, for they were fortunate in 
having at their disposal the skilled watch makers of 
southern Bavaria and Switzerland. The result was a 
large number of delays varying from a few minutes to 
as many as 21 days in operation and from the crudest 
to the finest workmanship. 

The British were keenly aware of the lack of such 
delays for use by individuals and demolition squads 
and had laid down a tentative specification for a suit- 
able fuze. 3 Their work proceeded simultaneously in 
Britain with development done by Division 19 and 
resulted eventually in a model based upon the Eureka 
clock, a mechanism used as standard equipment in 
British planes. 5 Neither this nor any of the German 
models which were made known to workers in Divi- 
sion 19 appeared satisfactory in meeting the rigorous 
requirements laid down by OSS and later confirmed 
by the Bureau of Ordnance of the Navy Department. 
These specifications included the following construc- 
tional and operational features, all of which were 
eventually met in the designs discussed below. 1 

1. The timing element, except in the multi-day 
models, was inexpensive, robust, and readily avail- 
able. 

2. The accuracy of operation was essentially that 
of the watch mechanism, and accurate setting was 
possible by retaining the function of both the hour 
and minute hands. 


mg approximately 2% in. square and 1% in. deep. 

4. It was unaffected by temperature changes be- 
tween — 4 and + 113 F, by severe vibration, by im- 
mersion in water to depths of as much as 70 ft, or by 
magnetic fields. 

5. The safety and starting means were so designed 
that they might be operated under water without 
danger of leakage. 

6. The safety pin was designed so that it could not 
be removed, if the device had fired or was about to 
fire. Its position was readily discernible at all times, 
and misoperation was prevented by an interlocking 
linkage. 

7. By means of a plastic window, the setting was 
visible, and a user could select any time desired. 
These times varied for the 12-hour delay between 
15 min and 11% hr, for the 24-hour delay between 
30 min and 23% hr, and for the multi-day delay be- 
tween 15 min and 6 days. 

8. The operation of an individual device could be 
tested by the user prior to actual use and the device 
reset without difficulty. 

The device, meeting the above rigorous specifica- 
tions and combining considerable robustness and re- 
sistance to adverse conditions, was eventually pro- 
duced in the 12-hour and 24-hour models in consider- 
able number by the Bureau of Ordnance and OSS. 
These were of interest and use also to the Engineer 
Board at Fort Belvoir, Virginia. Production was not 
without the usual difficulties and Section 12.6 of this 
report will indicate a few of the pitfalls which could 
be avoided in a future procurement. Nevertheless, 
the various models were considered as easily manu- 
facturable under good quality control and extremely 
reliable in operation. It was not believed that any 
foreign devices known to the division could equal the 
Mark 3 in its fulfillment of so many points. 

12.2 12 HOUR MODEL 1 2 

12.2.1 General Description 

Figures 1, 2, and 3 show the 12-hour firing device 
Mark 3 in three different views. In Figure 1 a phan- 
tom view is shown, from which it is clear how the 


74 


TWELVE-HOUR MODEL 


75 



Figure 1. Phantom view of parts of 12-hour model. 



Figure 2. Assembled view of 12-hour model. 



Fifflifi DEV ICC WAR* 3 

31 SAFETY m 



EI»ISH r I 

SITTING IN 1 HI 
DIRECTION Sf 

DO *ff v 

WIND TDD TICDTif 

mm*m nmnmwm cdntidi c «. 

i**iu. HL 


Figure 3. Back view of all models. 


mechanism functions and how safety and starting 
are provided. In Figure 2 and 3 are shown the front 
and rear views of the production models. 

Two knurled thumb screws projected from the 
case. The one in the back operated the safety, while 
the other located at one end started the device. The 
two plugs in the back of the case provided access for 
winding the watch movement and setting the delay. 
The main body of the case was of cast aluminum, 
while the back plate bearing the engraved instruc- 
tions was of iron, providing a certain amount of mag- 
netic protection. The front was covered by a trans- 
parent plastic window, held in place by a rubber 
gasket. For shipping, the firing end was closed by a 
plug, shown in the side of the case in Figures 2 and 3. 
For use this was removed and a suitable detonating 
train inserted for operation by the action of the 
spring-loaded striker. The case was made watertight 
by the use of gaskets, luting, and stuffing boxes. 

A watch movement of the cheap pocket watch type 
was selected because of its availability in quantity 
and robustness. The particular movement used was a 
back- wound and back-set type made by the New 
Haven Clock Company. This was selected in prefer- 
ence to a stem-wound and stem-set type, because the 
latter might stop, if the user failed to return the stem 
to the normal position after setting. The watch move- 
ment was slightly modified. The usual hour hand was 
replaced by a cupped disk having a narrow slot in its 
circumference (see Figure 1), and internal friction of 
the device was modified to increase reliability, while 
minor changes were made in other elements. The 
minute hand was retained to secure precision of set- 
ting, thus correcting a major fault of the usual me- 
chanical type delay mechanism. 

A study of Figure 1 will show details of the me- 
chanical operation. A sear held the striker with com- 
pression of the striker spring. One end of this sear was 
held by a fixed pivot, while to the other end was 
pivoted a latch. When the mechanism was cocked, 
the free end of this latch abutted against a roller car- 
ried by a fixed pivot and a tripping lever. The latch 
was tripped to release the firing device when the pro- 
jection on the lever end fell toward the center of the 
mechanism through the slot in the hour disk. The 
movement, under the action of a coil spring, released 
the latch and sear, and the device fired. It will be seen 
from Figure 1 that premature firing would be impos- 
sible because of the position of the safety directly in 
front of the firing pin. Premature operation would 
securely lock the safety and prevent its withdrawal. 


76 


CLOCKWORK TIME DELAY 


Figure 1 also shows the starting knob. When this 
was turned in a clockwise direction, it allowed a 
slight movement of the tripping lever, so that the 
projection on its end rested upon the smooth outer 
wall of the hour disk. In the same operation, a slight 
movement was imparted to the balance wheel of the 
clock, thus insuring the starting of the mechanism. 
Prior to operation, the inserted starting knob held 
the tripping lever free from the hour disk, allowing 
ready setting of it and preventing a misfire during 
that operation. 

12.2.2 Method of Use 

An operator would first assure himself that the 
watch was wound, the mechanism cocked, and the 
safety in the safe position. He would then remove the 
back plug and set the time delay by means of a small 
key provided with each device, while noting that the 
disk was the hour hand and the pointer the minute 
hand and that the figures on the dial progressed in 
the opposite direction from those of a standard 
watch. After replacing the plug securely against the 
waterproofing gasket and attaching a suitable firing 
end, he would turn the starting knob clockwise and 
then pull the safety out, locking it in the non-oper- 
ative position by a twist counterclockwise. Should it 
be desired to prevent stopping of the movement or 
replacement of the safety, both knobs were provided 
with soft alloy stems and could be broken off after an 
original placement. On the other hand, if the user 
wished to assure himself that the device was in satis- 
factory condition he could fire it prior to use and re- 
set it by inserting a suitable rod into the barrel and 
compressing the striker spring until the sear fell 
downward into position again. While maintaining 
this pressure and position, a turn of the starting 
knob counterclockwise would pick up and move the 
tripping lever through the slot in the hour disk back 
to its original position, where it would be retained by 
the starting knob while the hour disk was reset. The 
safety could then be re-inserted and the device would 
be in the same condition as originally delivered. 

The special features of this design which are be- 
lieved to be noteworthy are: the functioning of the 
starting knob to provide protection against prema- 
ture firing during setting, to allow resetting, and to 
insure operation of the clock movement ; the function 
of the safety which allowed underwater setting of the 
device with complete protection to the user; and the 
setting accuracy which was provided by the retention 
of the minute hand. 


12.3 24-HOUR MODEL 1 

This differed from the 12-hour model only in that 
the clockwork mechanism was so modified that the 
hour disk made a revolution in 24 hours instead of in 
12 hours. The only other change required was the 
partition of the scale into 24 major devisions instead 
of 12. The minute hand was retained as before, and 
the dial was provided with the usual minute divisions. 

The simplicity with which this could be made sug- 
gested that other time periods would be possible us- 
ing the same inexpensive New Haven movements. 
Models were constructed of a one-hour delay and of 
even shorter delays but were never produced. The 
one-hour delay was made by modifying the watch so 
that the hour disk made one complete revolution in 
one hour. The maximum delay period was 59 min, 
and the minimum setting was about V/2 min. Other- 
wise, except for a difference in the scale, all parts 
were identical with those used in the 12-hour delay. 
For delays of less than one hour, the rate of move- 
ment of the hour disk was altered by removal of the 
teeth from the escape wheel. Since the movement 
had a 17-tooth escape wheel, removal of 16 of these 
teeth increased the rate of the watch movement ap- 
proximately 15 times. The effective rate of such a 
modified watch was the average of two different 
rates : the usual one when the teeth were driving the 
balance wheel, which acted as a regulator, and a 
much higher rate when the escape wheel slipped 
where the teeth were missing. However, the fre- 
quency of alteration between these two rates was 
sufficiently high, so that the average rate of the 
watch was fairly constant. The maximum delay 
period obtained with this delay was min, the 
minimum setting about 0.1 min. Models of this type 
would probably have only limited usefulness in very 
special cases, mostly in the very short delays which 
are now so adequately met by the use of standard 
safety fuzes having remarkable reproducibility of 
burning per unit length. The increased precision 
gained by having a clockwork mechanism capable of 
functioning only over a span of one hour would prob- 
ably not be sufficient to recommend its preference 
over the standard 12-hour delay, whose accuracy 
was good. 

12.4 MULTI-DAY MODEL 1 

It was believed desirable to reach the upper limit in 
practicable timing, using the Mark 3 design. In going 
beyond a total delay period of 24 hours, a change in 


PERFORMANCE 


77 



Figure 4. Multi-day model. 

clockwork movement was required, for the inexpen- 
sive pocket watch type used in Sections 12.2 and 
12.3 did not have a spring sufficient to provide as- 
sured operation for a period beyond 24 hours. 

On the other hand, it was desired that the standard 
cast aluminum case of the Mark 3 model be retained, 
together with identical triggering and firing system. 
This meant the location of a robust and very com- 
pact 8-day clockwork. Two makes of watches were 
available for the purpose, both of them standard 
with the Navy for aircraft clocks: Elgin Model 5620 
and a Longine-Wittnauer. The former was definitely 
preferable because of its less fragile construction. 
Modifications required of this movement for the in- 
tended purpose were slight. The winding and setting 
shafts were altered to bring them out the back, thus 
providing the back winding and back setting feature 
already mentioned in Section 12.2. The hour hand 
was replaced by two disks concentrically mounted. 
The outer disk rotated once in the maximum delay 
period, which in practice was found to be not over 
6 days. The inner disk rotated once in 12 hours. The 
minute hand was retained and referenced with the 
usual hour and minute dial, so that setting was as 
accurate as with the 12-hour delay. The dial provided 
to reference with the day disk was subdivided into 
half-day divisions and was separate from the usual 
dial and placed above it. It was provided with a cir- 
cular opening through which the tripping lever and 
the hour and minute dial could be viewed. It is 
believed that Figure 4 shows this arrangement 
clearly. 


In operation the tripping lever was held by the 
outer disk during a period of days, until the slot in 
that disk permitted the lever to fall through, where- 
upon its projection rested upon the hour disk until 
the proper hour and minute arrived when the slot in 
that inner disk allowed the lever to continue its 
travel, releasing the sear and the striker. This model 
required in addition a slight reworking of the alumi- 
num casting standard with the 12-hour delay. 

If production were to be undertaken, a more robust 
movement would have to be provided. This could be 
done by reducing the weight of the plates in the 
movement and increasing the diameter of the shafts. 
The device would then withstand much rougher 
handling with no increase in weight or bulk. If an 
8-day delay were desired, a stronger main spring 
would have to be provided. Only experimental mod- 
els of this type were constructed in view of its late 
development in the war. 


12.5 

PERFORMANCE 

12.5.1 

Against Vibration and 


Magnetism 1 


Table 1 illustrates the independence which the var- 
ious models showed to vibration on a test board run 
at 1900 cycles per min and an amplitude of 0.020 in. 


Table 1 . Results of vibration test on clockwork 
delays. 


Model 

Delay 

setting 

Actual time 
elapsed 

Difference 
in minutes 

12-hr production 

unit 60 min 

59.7 min 

- 0.3 

24-hr, No. 2 

2 hr 

1 hr 56.5 min 

- 3.5 

24-hr, No. 5 

2 hr 

1 hr 59.75 min — 0.25 

1-hr 

59 min 

58.84 min 

- 0.16 

Multi-day 

3 hr 

2 hr 58.8 min 

- 1.2 


Table 2 shows the inconsequential effect of a mag- 
netic field provided by six J^-lb Alcomax magnets, 
each requiring a pull force of about 50 lb for removal. 


Table 2. Results of test for magnetic field protection. 


Model 

Delay 

setting 

Actual time 
elapsed 

Difference 
in minutes 

12-hr model 

Standard run 

11 hr 45 min 

11 hr 49 min 

+ 4.0 

Test run 

11 hr 45 min 

11 hr 48.75 min 

+ 3.75 

Multi-day model 

Standard run 

24 hr 

23 hr 59.0 min 

- 1.0 

Test run 

24 hr 

23 hr 59.25 min 

- 0.75 


78 


CLOCKWORK TIME DELAY 


12.5.2 Against Weathering and 
Humidity 8 - 9 

Tests included simulated tropical conditions in- 
volving exposure to an average temperature of 145 F 
and 95 per cent relative humidity for 28-hour periods 
and an intervening rest period of 16 hours. The usual 
change in timing which resulted thereby was well 
within the errors observed in Tables 1 and 2. Tests 
at high temperature with ordinary humidity (113 F) 
likewise produced no serious variation in performance 
(see Table 3). 


Table 3. Results of high temperature test with 
ordinary humidity. 


Model 

Delay 

setting 

Actual time 
elapsed 

Difference 
in minutes 

12-hr 

7 hr 30 min 

7 hr 31.4 min 

+ 1.4 

1-hr 

59 min 

58.96 min 

- 0.04 

Multi-day 

7 days 

7 days 0 hr 
7.75 min 

+ 7.75 


More serious than either of these conditions was 
the low temperature test. Here it was expected that 
trouble would appear because of freezing of the lubri- 
cant. Fortunately, this difficulty was entirely elim- 
inated by the use of a special synthetic lubricant 
manufactured by the Elgin Watch Company and 
known as No. 56A. 4 Before starting the watch, the 
unit was exposed to a temperature of — 20 F for ap- 
proximately 12 hours, given a 2-hour recovery at 
— 5 F, and then started and allowed to run at that 
temperature. Table 4 gives typical results. 


Table 4. Results of low temperature test. 


Model 

Delay 

setting 

Actual time 
elapsed 

Difference 
in minutes 

12-hr 

11 hr 20 min 

11 hr 22.5 min 

+ 2.5 

24-hr 

1 hr 

0 hr 59.0 min 

- 1.0 

1-hr 

59 min 

58.97 min 

- 0.03 

Multi-day 

6 days 

5 days 23 hr 

55 min 

- 5.0 


12.5.3 Against Rough Usage 

In these tests a unit was set for a delay of 30 min, 
but was not started and was then dropped three 
times from a height of 5 ft onto concrete. Some me- 
chanical damage to external features resulted, but 
no apparent damage to the mechanism itself. The 
watch was then started and run normally for 10 min, 
when the second half of the test was performed. The 
delay was set for one hour and started; it was then 


dropped three times from a height of 5 ft onto con- 
crete as before. Good performance following this 
drastic treatment was not always obtained, although 
there was very satisfactory behaviour of the vast 
majority of the units. 

12.6 MANUFACTURE 1 6 

The specifications 6 laid down for the original man- 
ufacturer of the 12-hour model were arrived at 
jointly by the division’s contractor and the Bureau of 
Ordnance. They appeared satisfactory, provided 
they were adhered to by rigid quality control. One 
of the services given by the division was critical ad- 
vice to the manufacturer by the original developer of 
the Mark 3 design. As a result of this advice and 
Navy concern with reported failures 7 in the field, the 
early production was inspected and, in part, re- 
worked. This served to eliminate a number of points 
which had needlessly been allowed to crop up be- 
cause of inadequate inspection at the start of pro- 
duction. These points included such defects as leak- 
age under water pressures of less than 20 ft, sticking 
trip levers, serious misassembly of the movement in 
the case, slipping main springs, and so forth. It ap- 
peared that none of these defects were caused by the 
design but rather to the lack of appreciation at the 
start by the manufacturer of the importance of close 
adherence to the specifications. Even so, the admit- 
tedly improved production would be estimated to 
give 85 per cent performance as it stood. Any future 
production would presumably be based upon the 
amended specifications, and with this word of cau- 
tion should encounter no difficulty. The testing of a 
number of production mechanisms by the central 
laboratory of the division entirely confirmed this 
judgment. 8 - 9 

Both OSS and the Navy Department insured the 
delivery of the Delay Firing device to the field in 
perfect condition by packaging them in hermetically 
sealed tin containers. Whether or not this require- 
ment was essential, it did provide additional pro- 
tection. 


12.7 CONCLUSION 

It was demonstrated that clock-operated delays 
based upon cheap, readily available movements 
could be produced in numbers to cover a wide range 
of timings. Models tested covered the range from 


CONCLUSION 


79 


0.1 min to 23 hr, using a cheap movement and a 
range of 15 min to 6 days using a more expensive 
movement. 

Delays having nominal timings of 12 and 24 hours 
were manufactured in quantity. They proved highly 


accurate and insensitive to temperature changes, 
rough handling, and extremely unfavorable weather 
conditions. It is believed that a useful fuze was de- 
livered and that a need of both the Army and the 
Navy was thereby fulfilled. 



Chapter 13 

BASES FOR TIME DELAY FUZES 


13.1 INTRODUCTION 

In preceding chapters in this volume a number of 
time delay fuzes have been described : the clockwork 
type, which was both accurate and inexpensive and 
suited for use either below or above water (Chap- 
ter 12), and the SRA, the SRI, and the Mark II 
Pencil, which were relatively inaccurate but easy to 
produce in quantity and very cheap (Chapters 9, 10, 
and 11). 

The latter type of fuze was entirely unsuited for 
use below water, and the need therefore existed for a 
counterpart to the Pencil which could be used for 
marine demolitions. Such a fuze already existed in 
the so-called AC delay (Acetone Celluloid), a British 
development. This fuze was produced in the United 
States by OSS, following exactly the British specifi- 
cations. It is described in Section 13.2 only because 
the division’s central laboratory modified the fuze to 
provide both shorter and longer timings than the 
original specifications gave. The remainder of the 
chapter summarizes the negative experience of the 
division’s contractors in a search for a system which 
could supplant either the Pencil time delay or the 
AC delay in scope, cheapness, and usefulness and 
which would have the additional features of better 
reproducibility and greater independence to temper- 
ature change. 

Section 13.3 dealing with organic fiber delays is of 
interest primarily because the systems investigated 
had a zero temperature coefficient. Section 13.4 de- 
scribing magnesium alloy delays is interesting be- 
cause of the compactness and simplicity of design. 
The other sections deal with physical and chemical 
systems which did not prove profitable or were un- 
explored. 

13.2 MARK I AC DELAY 

13.2.1 The Standard Delay 

This device consisted of a heavy brass tubular 
body threaded at both ends to receive at the bottom 
a primer and detonator system and at the top a brass 
screw cap. Close to the bottom was located an auxil- 
iary part consisting of a firing pin held under spring 
tension by a celluloid washer and poised directly 
above the primer cap. In the chamber above the 


washer was located a glass ampule containing an or- 
ganic solvent mixture. The cap at the top of the fuze 
was provided with a screw knob which on being 
turned moved a piston protected by a rubber sheath 
down against the glass ampule. This eventually re- 
sulted in crushing of the ampule and releasing of the 
organic solvent for action on the celluloid washer. 
This attack consisted entirely of physical softening 
and solution and proceeded to a point where the 
washer was so weakened that it could no longer sup- 
port the firing pin under the spring tension; there- 
upon the device fired. Its solid brass construction in- 
sured waterproofness, even to depths as great as 
70 ft. 6 

There was some effect due to position 5 but it was 
found that even if the fuze were mounted with the 
ampule down when crushed so that the liberated or- 
ganic solution never actually wetted the celluloid 
disk, firing nevertheless took place, although after a 
much prolonged interval due to the attack of the or- 
ganic vapors on the washer. The temperature effect 
was considerably smaller than that encountered in 
the Mark I P encil (SRA-3) and in any case could not 
be expected to be as serious, inasmuch as the AC 
Delay was intended primarily for marine use where 
the temperature range would be limited presumably 
to between about 30 and 80 F. 

As in the case of the Mark I Pencil, different tim- 
ings were provided by variations in ampule contents. 
The British and American practice was to give the 
user with each delay a kit of several ampules contain- 
ing differently colored solutions. The user could 
thereupon select the ampule for his purpose and 
assemble it in the delay. Table 1 is a time-temper- 
ature chart of recommended operational timings. 


Table 1 . Recommended operational timings for 
AC Delays. 


Temp 

Red 

hr 

Orange 

hr 

Yellow 

hr 

Green 

hr 

Blue 

hr 

Violet 

days 

Temp 

41 F 

6* 

12* 

23 

34 

80 

9 

5 C 

50 F 


11 

19 

29 

61 

7 

10 C 

59 F 

5 

91 

16 

24 

48 

5 

15 C 

68 F 

41 

8 

14 

20 

39 

4 

20 C 

77 F 

4 

7 

12 

16 

32 

3 

25 C 

86 F 

31 

6 

10 

14 

26 

2 

30 C 


The effect of position on the above timings was de- 


80 


ORGANIC FIBER DELAYS 


81 


termined using green ampules. On horizontal activa- 
tion, a mean value of 18.0 hr + 6 per cent was ob- 
tained; on vertical activation a mean of 36.2 hr; and 
on activation at an angle of 15 degrees a mean of 
18.4 hr. 5 It would seem desirable in field use that the 
AC delay should be activated in a horizontal or 
downward position, following which its position 
could not be expected to have much influence on the 
timing. The reproducibility of these delays under 
such conditions of activation and use was remark- 
ably good with the variance (see Section 9.11.2) being 
about 8 per cent. 

In the interest of uniform performance between 
British and American production of the Mark I AC 
delay, producers in Britain and the United States 
both used the same source of celluloid disks. Some 
research was done in the division’s central laboratory 
to discover a substitute for celluloid having improved 
qualities and being capable of better reproducibility 
in different batches. This work 3 was not particularly 
successful. American celluloid behaved very badly 
and was unreliable from batch to batch. Most plas- 
tics tried also had unfortunate characteristics such as 
sensitivity to humidity, brittleness, and so forth, 
which gave an excessive per cent variance. Of all the 
materials tried only butacite (polyvinyl butyral) ap- 
peared to be a possible competitor to well-cured cellu- 
loid. Should production of the AC delay be under- 
taken again in this country, it would be advisable to 
locate a suitable source of this material and give 
American production independence from British 
supply. 

13.2.2 Short Time Mark I AC Delay 2 

From Table 1, it is apparent that the shortest tim- 
ing for which the Mark I delay is suited is not ex- 
pected to be less than 3 Yi hr even at a temperature 
of 86 F. For training purposes this was not satisfac- 
tory. It was desired that a shorter timing be provided 
so that men might familiarize themselves with the 
operation of the delay and still have the opportunity 
of seeing it function. 

The division’s central laboratory successfully met 
the problem by devising a new ampule solution and 
designing a new plastic disk to replace the celluloid. 2 
A study of a variety of organic solvents disclosed that 
only methyl formate gave timings shorter than the 
Red timing quoted above in which acetone was the 
solvent. This timing was obtained most advanta- 
geously when the celluloid disk was replaced with 


cellulose acetate disks molded in an injection molding 
machine, through the courtesy of the Naval Ord- 
nance laboratory at Silver Springs, Maryland. The 
resulting performance expected of the short time de- 
lay was as follows: at 32 F, 75 min; at 77 F, 35 min; 
at 112 F, 13 min. Variations of about 25 per cent 
could be expected. In spite of this rather high vari- 
ance, the devices were useful for the intended train- 
ing purposes but were never issued to the field. 

13.2.3 Long Time Mark I AC Delay 4 

The need was expressed for a special operation re- 
quiring a delay period of several weeks. As will be 
seen from Table 1, the standard production of the 
Mark I delay could be expected to give a maximum 
timing of 9 days at 41 F. The central laboratory of 
the division therefore developed a new ampule solu- 
tion for providing longer times. Table 2 gives the re- 
sults of this work. 

Table 2. Summary of timing data — long time AC 

Delay ampules. 


Composition in weight per cent 


Ampule 

designation 

Dimethyl 

phthalate 

n-butvl 

lactate 

Temp 

Mean 
value 
in weeks 

Per cent 
spread 

7 

62.2 

37.8 

40 C 

0.7 

18 




25 C 

1.8 

24 

8 

83.4 

16.6 

40 C 

1.5 

20 




25 C 

3.7 

8 

9 

92.5 

7.5 

40 C 

2.0 

10 




25 C 

5.6 

11 

10 

99.0 

1.0 

40 C 

2.6 

7 




25 C 

9.1 

11 


The above compositions were selected after a study 
of a variety of esters and mixtures of them. Since the 
operational requirement for the devices did not spec- 
ify a very high degree of precision and performance 
timing, the considerable percentage variation was 
not felt to be a severe deficiency. The timings were 
obtained using the standard celluloid disk of the 
Mark I AC delay. 

13.3 ORGANIC FIBER DELAYS 

The search for a system independent of temper- 
ature and having good reproducibility included work 
on organic fibers. It seemed that nylon might be a 
likely choice since it could be made reproducibly in 
fibers of known diameter and was a pure chemical 



82 


BASES FOR TIME DELAY FUZES 


substance. Also it was resistant to cold flow over 
periods of years wdiile under a strain representing a 
large fraction of its breaking load. Tests with nylon, 
however, did not produce the hoped for results. 

Work on other synthetic fibers of the regenerated 
cellulose type appeared more promising and is de- 
scribed in two parts of this section. While it was pos- 
sible to construct a laboratory model of a delay based 
on these reproducible organic fibers, it was found 
that the timings provided by them were very greatly 
affected by a number of factors including the chem- 
ical composition of the solvent, the diameter of the 
fiber, the twist of the fiber, the per cent loading, and 
the area of the fiber under attack. In view of these 
tremendous complexities and the success which at- 
tended the Mark II development described in Chap- 
ter 10, the work was abandoned. It is felt that there 
is no promise in delays based on these systems, and 
they are recorded here to prevent wasteful repetition. 

13.3.1 Nylon 7a * 8 

The solvent found most effective for nylon was un- 
fortunately a 7 per cent nitric acid solution saturated 
with potassium nitrate, which attacked the nylon by 
its hydrolytic action on the amide linkages. The 
presence of the potassium nitrate gave a system 
which had essentially a zero temperature coefficient 
due to the high positive coefficient of solubility of the 
salt. Unfortunately, at low temperatures a slush of 
crystals formed by the deposition of nitrate tended 
to prevent contact with the nylon cord and gave ex- 
tremely variable results. It was found also that vari- 
ations in timings were very large for small variations 
in filament diameter, so that a 20-mil nylon wire 
was many times more resistant than a strong nylon 
cord of the same diameter composed of 306 individual 
filaments. 

The only other solvent for nylon appeared to be a 
methyl alcohol solution containing 20 per cent of 
calcium chloride. This system did not have the very 
low temperature coefficient of the nitric acid system, 
although it did provide longer timings. 

Another drawback to the nitric acid system, aside 
from the difficulty of handling such a strong chemical 
in the field, was its inability to provide a maximum 
timing of longer than about 20 min. This did not be- 
gin to cover the range of the Mark I Pencil. It was 
one additional reason for the decision to abandon 
nylon. Table 3 illustrates the performance which 
was obtained. 


Table 3. Performance of nylon cord 8Z 7. IS. 


Nylon 

cord 


Breaking time in minutes 

Solvent 

2 C 

26 C 

60 C 

8Z7.1S 

25% HN0 3 

11 

5.3 

0.2 

a 

25% HN0 3 

Saturated with KN0 3 

34 

8.2 

1.3 

u 

10% hno 3 

Saturated with KN0 3 

9 

10 

5 

u 

7% HN0 3 

Saturated with KN0 3 

12 

11.6 

7 


The remarkable effectiveness of the added potas- 
sium nitrate is clearly seen from Table 3. With it a 
temperature coefficient approaching zero would be 
unobtainable. 

13.3.2 Cordura 7a 8 

It was found that a high tenacity regenerated cellu- 
lose fiber woven in cords and known as Cordura was 
susceptible to attack by sodium hydroxide solutions 
with essentially zero temperature coefficient. This 
remarkable happening appeared to be the result of at 
least two competing chemical reactions which were 
not explored. 

The fiber was a standard production item and as 
used was two-ply, had a twist and ply of 10. 5Z; 7.5S, 
a tenacity of 36 % lb, and a 10 per cent elongation. 
When such a fiber was loaded to 30 per cent of its 
breaking load and immersed in a solution of sodium 
hydroxide varying between 4.2 and 5.2 per cent, a 
near zero coefficient resulted at 10 and 20 min break- 
ing times. This ideal state was apparently reliable 
only with the conditions given, for a variation in one 
per cent of sodium hydroxide gave serious variations 
in timings and a complete loss of the zero temper- 
ature coefficient. Moreover, performance was very 
sensitive to the per cent loading, and since Cordura 
showed a tendency to elongation on standing under 
stress, a variable per cent loading was inevitable. 
Finally, it was not possible to alter the timing by 
dilution of the sodium hydroxide solutions. Added 
sodium chloride and glycerol or similar diluents, 
while somewhat effective in this way gave variable 
results, and it appeared that no timing of more than 
40 min could be expected from the system. Also, the 
effect of twist was found to be considerable, but not 
of a nature to correct any of the deficiencies noted 
above. The substitution for sodium hydroxide by 
other chemicals such as potassium hydroxide, lith- 
ium hydroxide, and tetramethyl ammonium hy- 
droxide was also ineffective. 


MAGNESIUM ALLOY DELAYS 


83 


For the many reasons given, the system was aban- 
doned. Typical of the data obtained is Figure 1. Even 
had the system been usable, the problem would have 
existed of finding a suitable ampule to contain the 
strong alkali over indefinite storage. This appeared 
possible in the use of special Corning alkali resistant 
glass. It can be seen that the area bounded roughly 
by 32 and 35 per cent breaking load and 8 to 15 min 
in time had essentially a reliable performance inde- 
pendent of temperature. 



Figure 1 . Effect of loading on breaking time for Cor- 
dura in 5.2 per cent sodium hydroxide. 


13.3.3 Fiber G 7a 

This material differed from Cordura only in the 
method of manufacture. Tests with it gave better 
reproducibility at high times but poorer at low times. 
It also was entirely comparable to Cordura in pos- 
sessing a zero temperature coefficient in a limited 
range and having great sensitivity to the numerous 
variables already mentioned. Figure 2 indicates the 
relationship between breaking time and loading time 
for this material in the best solvent, namely 10 per 
cent sodium hydroxide. 

13.4 MAGNESIUM ALLOY DELAYS 9 

13.4.1 The Alloy 

It seemed possible that a suitable alloy of mag- 
nesium might be discovered which would be stable 
under atmospheric humidity but which would spon- 
taneously dissolve in the presence of an electrolyte. 
This was based upon the functioning of the alloy as a 


couple, in which the elements of an electrochemical 
cell were present. In some respects it resembled 
closely the idea underlying the Electrolytic Arming 
Disk (see Section 8.4.2) and the Mark II Pencil (see 
Chapter 10). 



TIME IN MINUTES 


Figure 2. Effect of loading on breaking time for fiber 

G in 10 per cent sodium hydroxide. 

From the laboratories of the Aluminum Company 
of America, a material was obtained which had these 
properties and consisted of: magnesium, 99.7 per 
cent; iron, 0.2 per cent; and nickle, 0.1 per cent. 
The fundamental process of all devices based on this 
alloy was the controlled corrosion of it by the elec- 
trolyte comprised of salts in aqueous solution. A 
number of salts were investigated of which ammo- 
nium chloride appeared to show the greatest advan- 
tage. This was explained by the following equations: 

Mg + 2 HOH Mg{OH\ + H 2 and 

MgiOH ) 2 + 2 NHtCl -> MgCU + 2 NH,OH 

Because magnesium hydroxide is a stronger base than 
ammonium hydroxide the second reaction took place 
and the insoluble magnesium hydroxide which would 
otherwise accumulate was removed from the reaction 
exposing fresh surfaces for further attack. 

Other considerations would indicate that, in either 
strongly acid or strongly basic solutions, magnesium 
would be too reactive and the reaction would tend to 
have a high temperature coefficient. The pH range 
provided by ammonium chloride was the most fa- 
vorable which could be found. Using this metal and 
this system as the basis, two types of delays were ex- 
plored to a point which indicated that neither would 
be likely to yield a successful competitor to the 



84 


BASES FOR TIME DELAY FUZES 


Mark I or the Mark II Pencil. These types are given 
in the two following sections. 

13.4.2 Barrier or Disk Type 

In this application the electrolytic solution was 
brought into contact with the timing element of mag- 
nesium alloy which was in the form of a disk or a 
barrier separating the electrolyte from a dry add- 
water type of electrolytic cell. If the barrier disk of 
special alloy were of a predetermined thickness and 
had a predetermined exposed area, the time required 
for errosion of this disk was found to be fairly con- 
stant. Eating away of the barrier allowed the excess 
electrolyte to penetrate into the underlying electro- 
lytic cell, of which magnesium served as the anode 
and a silver wire coated with a thin layer of a fused 
silver chloride served as the cathode. When contact 
was established, a current was produced by this cell 
which was sufficient to fire an electric squib (Hercu- 
les Blasting Cap 100-24B). Such a cell could be 
counted upon to deliver for a period of one min at a 
resistance of one ohm between 600 and 350 ma of 
current at 1.86 volts. 

Several different designs were built utilizing this 
electric firing system, and of them the most success- 
ful contained the ampule of ammonium chloride so- 
lution in a gas-tight chamber with crushing provided 
in the manner of the AC delay (see Section 13.2). It 
will be noticed that hydrogen is evolved by the re- 
action and use was made of this to build up pressure 
in the gas-tight chamber and to provide a positive 
means of forcing the electrolyte through the eroded 
barrier onto the poles of the firing cell. No design was 
ever successful in providing operation independent 
of position and, from a field view point, this was so 
serious that the system was abandoned. It appeared 
also that unless the electrolyte was delivered to the 
firing cell instantly, the serious drain on that cell’s 
potential gave frequent misfires. 

Other considerations also led to the abandonment 
of the idea which is illustrated in Figure 3. 

13.4.3 Shear or Tension Type 

Much simpler than the barrier type were models 
based on the use of the special alloy as a wire, 
mounted either in shear or in tension, supporting 
mechanically a firing pin held against a compressed 
spring. The similarity to the Pencil time delay will be 
apparent. Figure 4 illustrates this type of design. 



UNEXPLORED OR UNSUCCESSFUL SYSTEMS 


85 



Figure 4. Shear type magnesium alloy delay. 


In this model the deficiencies of the electric method 
of firing were eliminated but new difficulties arose in 


assuring that the alloy member was adequately 
bathed by fresh electrolyte solution during the re- 
action period and in using magnesium wires of di- 
ameter sufficient to prevent cold flow on long stand- 
ing, while still being small enough to give useful time 
delay periods. The per cent variation expected from 
such a system was somewhere between 6 and 13, a 
distinct improvement over the Mark I Pencil ; never- 
theless, the design was one which would operate only 
in a vertical position, which would be very critical to 
manufacturing procedures (particularly to the di- 
ameter and dimensions of the stressed magnesium 
element), and which would show no remarkable ad- 
vantages. Its performance is illustrated in Table 4 
using an alloy shear pin of diameter 0.065 to 0.066 in. 
and 0.20 ml of electrolyte solution, one molar in 
acetic acid, sodium acetate, and ammonium chloride. 


Table 4. Operational characteristics of shear type. 


Temperature 

Mean time 

% Deviation 

39 C 

140 min 

10.7 

24 C 

227 min 

13.7 

10C 

385 min 

9.3 

6 C 

561 min 

8.7 

2 C 

559 min 

6.3 


These figures illustrate the increasingly good per- 
formance at low temperatures and, on the whole, 
remarkable independence of the essentially chemical 
reaction from temperature. In spite of these good 
features, the system did not have sufficient merit to 
warrant its serious consideration as a universal time 
delay comparable to the time Pencil. However, for 
very special uses where lightness and compactness 
are important features, a delay could be devised in 
which the special magnesium alloy might have great 
advantage over any other known system. Details of 
such a delay were worked out but it was never put 
into production. 1 

13.5 UNEXPLORED OR UNSUCCESSFUL 
SYSTEMS 

A number of ideas came to the attention of the 
division. Many of them were never worked upon, and 
others were only partly investigated. They are re- 
corded here as possibilities for future evaluation. 

1 . Bimetallic Electrolysis. A system was proposed 
consisting of two elements of cadmium and zinc re- 
spectively. Upon the addition of an electrolyte the 
spontaneous solution of the zinc might be useful as 


86 


BASES FOR TIME DELAY FUZES 


the basis of a time delay. This was not investigated 
in view of the success of a similar system in the 
Mark II Pencil. 

2. Cold Flow of Metals. Some work was done in 
the United Kingdom and by the division 9 on zinc 
and lead employed as metal sheets through which a 
striker point was caused to penetrate by spring ac- 
tion. A time delay system could thus be devised de- 
pending upon the force of the spring and the thick- 
ness of the metal sheet. Unfortunately both lead and 
zinc displayed an extreme sensitivity to temperature 
and shock and the system was abandoned. 

3. Gas Leak. 10 Considerable work was done in 
Britain on a device consisting of an evacuated cham- 
ber sealed from the air by a metal tear strip cover, 
beneath which lay a ceramic disk of unglazed porce- 
lain. The other end of the evacuated chamber was 
provided with a click diaphragm similar to that used 
in the Sympathetic Fuze (see Chapter 8). Removal 
of the metal cover allowed the atmosphere to flow 
through the pores to the ceramic disk and eventual^ 
to build up the pressure inside the evacuated cham- 
ber to a point where the sensitive bimetallic disk 
would snap and fire. Basically the system was sound 
in that the laws governing diffusion are practically 
independent of the ordinary temperature range ; how- 
ever, manufacturing difficulties were very severe and 
the problem of reproducing porous plugs was never 
overcome. 

4. Liquid Leak. The use of constant viscosity 
liquids such as silicone flowing through minute ori- 


fices could be used as a basis for a time delay either 
mechanical or electric. Some work of this sort has 
already been mentioned (see Section 8.4.3) as a gen- 
eral scheme for a number of delays covering a wide 
range of timings. 

5. Swelling of Rubber. It was found possible to de- 
vise a very inaccurate but certain delay based on the 
well-known property which rubber has of swelling 
when immersed in organic liquids such as gasoline. 
For special operational uses such a system was recom- 
mended. 

6. Battery Exhaustion. It was suggested that a 
striker held by an electromagnet would fire upon ex- 
haustion of the battery supplying energy to that 
magnet. The well-known variations in batteries and 
their extreme sensitivity to age and temperature 
made the system seem unlikely. 

7. Diurnal Temperature Change. For a delay of 
one or more days, use could be made of the uncertain 
but inevitable temperature change which generally 
occurs with sunset. This type of delay would be very 
crude and limited to special uses in special geographi- 
cal locations. 

Much energy and several years of work were ex- 
pended by division personnel in a search for an im- 
proved time Pencil and for new time delays in gen- 
eral. Those which were successfully developed were 
the Mark II Pencil, the improved Mark I Pencil, the 
clockwork delays, and the modified AC Delays. None 
of the systems given immediately above can in the 
opinion of the writer compete with these. 


Chapter 14 

RADIO-CONTROLLED SWITCH 


14.1 INTRODUCTION 

At the request of OSS and with the cooperation of 
the Signal Corps, Division 19 embarked on a pro- 
gram to develop a radio-controlled switch for the re- 
mote activation of explosive or incendiary materials. 

The first operational requirement suggested that 
the switch be operated on a frequency close to 100 kc 
by a fixed radio station. It was required also that the 
switch have a maximum life after being planted and 
activated, which meant a design imposing only a 
small drain on the dry cell batteries which would be 
required to keep the set in operation. Secondly, it was 
desired that when these batteries had exhausted 
themselves and the set was no longer able to function 
on receiving the appropriate radio signal, it should 
automatically destroy itself. A third major require- 
ment called for mechanical firing to be accomplished 
upon receipt of the proper signal, but only after an 
interval of sufficient duration to prevent the acci- 
dental tripping of the switch by enemy sweeping of 
the air or by accidental natural disturbances (Sec- 
tion 14.2). 

A switch meeting these requirements had reached 
an advanced state of development when the opera- 
tional picture altered and the need for a set operated 
on 100 kc vanished. In its place appeared a need for a 
radio switch to function on receipt of a signal of 
about 100 megacycles. Transmitting equipment ca- 
pable of providing this signal existed in all standard 
bombers of the United States and Great Britain, and 
operations were visualized in which radio switches 
previously planted by ground forces would be acti- 
vated by on-coming bombers when they were close to 
their target. On activation the switches would fire 
flares, which would mark the target more precisely or 
delineate the front line of operations, thus preventing 
accidental and premature dropping of bombs on 
friendly troops. Another use conceived for such a 
switch included the marking of air fields at night 
(Section 14.3). 

The last phases of the program were concerned 
with the development of a similar switch to be oper- 
ated by a transmitter on the ground in a range of 3 to 
8 megacycles. Such a switch would be of interest to 
the Corps of Engineers and could be used to detonate 
explosives planted prior to a retreat (Section 14.4). 

The problem was not unique with Division 19, for 


the Signal Corps had similar devices under develop- 
ment and some of them in production and use. The 
work was not entirely repetitious, however, because 
of the tremendous effort made to keep volume and 
weight of the radio switch to an absolute minimum, 
and to provide the longest possible shelf life and self- 
destructive features. Since the personnel of Divi- 
sion 19 were not by background equipped to deal 
adequately with a radio problem, the bulk of the 
work was very generously done in Division 13 with 
the aid of a cooperative committee comprising the 
two divisions and the interested liaison officers. 

The only one of this family of switches which was 
produced was the one to be operated by aircraft at 
100 megacycles, of which approximately 1,000 units 
were manufactured by OSS. 

14.2 OPERATION AT 100 KILOCYCLES 1 

This unit consisted essentially of a loop, a metal 
housing for a radio chassis relay, a battery pack, an 
electrolytic cell, and a self -destructive mechanism. 
The block diagram shown in Figure 1 illustrates the 
operational scheme. 



Figure 1 . Block diagram of operational scheme, SE 
unit. 


The receiver unit was cased in a sealed box having 
a volume of 216 cu in. and carried an insulated loop 
measuring 6 x 9 x 3^6 i n * attached by clips. Of the 
total volume, nearly one-half was provided for the 
electrolytic cell and its accompanying mechanical 
detonating train and a charge of plastic explosive or 
incendiary material. The loop tuned to the operating 
carrier frequency of the transmitter when located in a 
field strength of 100 microvolts per meter or more 
applied a voltage on the grid of the first radio fre- 
quency amplifier stage. Another stage following this 
increased the amplitude sufficiently to reduce the bias 
on a direct current amplifier, thus causing plate cur- 


' RESTRICTED^ 


87 


88 


RADIO-CONTROLLED SWITCH 


rent to flow in an output resistor. So long as this was 
low, the B battery current passing through a relay 
coil kept the relay armature open, but as soon as the 
field strength reached 100 microvolts per meter the 
current passing through the relay coil increased to 
the point where the relay armature closed. Closure of 
this connected a battery circuit involving the so- 
called electrolytic cell. This was provided to prevent 
premature firing of the switch by accidental signal- 
ing. So long as a constant signal of the proper wave 
length and field intensity was received by the loop, 
a current would pass in the electrolytic cell, eventu- 
ally operating it. 

This cell consisted of a thin glass bulb filled with 
dilute sulfuric acid and containing two platinum 
electrodes. It was mounted in two bayonet-type 
sockets under a tension of 8 lb and was an integral 
part of a mechanical firing train. Passage of the elec- 
tric current through the cell resulted in the electroly- 
sis of the dilute acid with the production of hydrogen 
and oxygen gas. Collection of this continued in the 
glass bulb to the breaking point, whereupon the me- 
chanical initiating system of the device operated and 
the charge was fired. The exact performance of the 


electrolytic cell depended on the temperature, the 
diameter of the bulb, and more critically on the di- 
ameter of a bubble of air sealed in the cell in its man- 
ufacture. In Figure 2 11 the performance obtained as 
a function of temperature and bubble diameter is 
recorded. 

It is apparent, for example, that with a bulb hav- 
ing a bubble diameter of }/% in. at 74 F receipt of the 
proper signal for 5 min would be required before the 
switch would perform. In this way complete safety 
was provided against accidental triggering by enemy 
or natural means. 

Should the small battery pack of the radio switch 
become exhausted prior to receipt of the proper sig- 
nal, the B and filament voltages would drop suffi- 
ciently on the amplifier tubes to allow the relay ar- 
mature to close as before, bringing about the self- 
destruction of the unit. Tests with this type of switch 
showed that it would operate over a distance of at 
least 30 miles provided it were not shielded by large 
metal objects. The ambient field strength could be 
safely estimated by a user in advance and the device 
adjusted so that arming it did not entail danger. Fur- 
thermore, adjustments could be made in individual 



TIME OF RUPTURE -MINUTES 

Figure 2. Performance of special electrolytic cells at various temperatures. 



OPERATION AT 100 MEGACYCLES 


89 


sets to provide functioning between 95 and 120 kc 
with increase in sensitivity and decrease in selectivity 
at the higher figures. A total weight of 8 lb, including 
2 lb of batteries, gave a switch having a life after 
planting of approximately one week. 

14.3 OPERATION AT 100 MEGACYCLES 9 

14.3.1 Single Tube Model 

Using a proposal of a circuit containing a super- 
regenerative gas tube such as had been used for the 
control of model airplanes in flight (triode type QF-6), 
a circuit was designed operating at about 90 mega- 
cycles. 10 Using the single tube and very small batter- 
ies, it was believed that a unit occupying not more 
than 18 cu in. and having an operating life of about 
one week could be devised. This would be a great im- 
provement over the rather bulky 100-kc model and, 
moreover, would more closely approach field require- 
ments. Unfortunately, attempts to construct a 
switch based on this single QF-6 tube were entirely 
unsuccessful due to the breakdown of the tube under 
the conditions imposed by operation at frequencies 
close to 100 megacycles. It appeared that the QF-6 
had been designed primarily for use at 60 megacycles. 

Attempts to develop a new tube which would suf- 
fice for the higher frequency ranges were unsuccess- 
ful, and the early designs were abandoned. 2 * 3 * 4 This 
was not before it had been discovered that changes in 
sensitivity could be caused by surrounding objects 
due to absorption, reflection, and radiation and that 
there were limitations in the mechanical and electri- 
cal components. Notable among these was the re- 
quirement of delayed action, which in the 100-kc 
model had been met by the electrolytic cell. This was 
not considered feasible for use with the 100-mega- 
cycle unit because of its fragility and irreversibility. 

The suggestion that the armature of the relay be of 
a pendulum type suspended in a vertical position, so 
that its time cycle would be sufficient to cause it to be 
inactive during momentary electrical impulses did 
not on trial prove satisfactory. Moreover, it imposed 
a positioning of the switch, which was not felt desir- 
able. On the other hand, a delay provided by a meter 
type movement was found to be quite practical, in- 
sensitive to vibration, and, when provided with mag- 
netic damping, unresponsive to a plate current caused 
by static surge in the neighborhood of sec, a period 
which should have been ample to take care of any 
such accidental interference. 


The switch was also provided with a booby-trap ar- 
rangement to prevent its being moved, and arming 
was accomplished by the use of a special key which 
would be disposed of by the operator. Any attempt 
to interfere with the set by the insertion of a substi- 
tute key would result in instantaneous operation, 
since an electric contact directly to a small internal 
charge of plastic explosive would thereby be made. 
Operation of the set on exhaustion of the batteries 
was as described in the earlier devices. 

Even though the one-cell model based on the QF-6 
tube proved impractical, it nevertheless contributed 
features to the later successful design. 5 

The circuit of this switch is shown in Figure 3. Al- 
though only a single tube was used, operation of the 
circuit was complex. It functioned simultaneously as 
a self-quenching super-regenerative detector and as 
an audio-frequency gas tube relaxation oscillator. 
Upon receipt of a signal of proper frequency and in- 
tensity, the plate current dropped to a fraction of its 
normal value, causing the relay to close the external 
circuit. 

ANTENNA 
5" WIRE MOLDED 



Figure 3. Circuit diagram of radio-controlled switch. 


14.3.2 Two-Tube Model 

When it became evident that the circuit mentioned 
above would not be satisfactory, consideration was 
given to one employing other types of tubes. A new 
circuit was designed to operate on an r-f carrier which 
was amplitude-modulated with an audio tone of pre- 
determined frequency. It would thus not operate on 


90 


RADIO-CONTROLLED SWITCH 


an unmodulated carrier, and the audio-frequency 
selective circuit and time delay carried in the switch 
made false operation unlikely. Models of this type 
having a volume of about 60 cu in. and weighing 
about 2% lb, including batteries, had sufficient sensi- 
tivity to be operated by an SCR-522 transmitter 
from a plane at an altitude of 10,000 ft, 10 miles 
away. The essential circuit of this switch is shown in 
Figure 4. 


ANTENNA 
(SHORT WIRE) 



Figure 4. Circuit diagram of two-tubed radio-con- 
trolled switch. 


Two tubes were employed: a type 957 super-regen- 
erative detector, and a type 1S5 having both a diode 
and pentode section. The diode was used to rectify 
the audio-output voltage from the detector. The di- 
rect current voltage so obtained biased the grid of the 
pentode section negatively and reduced the current 
in the plate circuit materially, thus the relay nor- 
mally held was released upon the receipt of the tone- 
modulated control signal. 

Because the detector load impedence was an anti- 
resonant circuit, operation of the switch depended 
upon a prescribed narrow range of audio-frequencies. 
In this feature lay the safety of the circuit. In addi- 
tion, the network provided against false operation by 
giving a delay of about 250 millisec. Operated at an 
ambient temperature of 70 F, this circuit had a maxi- 
mum life of approximately 80 hours. Increase in bat- 
tery load would, of course, increase this time. 


Detection of the switch due to radiation from it 
was not easily accomplished, for it did not produce a 
characteristic whistle when the receiver frequency 
oscillator was turned on. The accuracy of tuning was 
about ±100 kc, and, in view of the broad response 
characteristics of the switch, it was considered suf- 
ficient. 

The theoretical range would depend upon the field 
intensity; where tuning was accurate, the switch op- 
erated on a signal of 200 microvolts per meter or less. 
Little or no attenuation due to surrounding objects 
would be expected. Table 1 gives the performance 
from planes at different altitudes. 

Table 1. Performance of two-tube model at various 
altitudes. 5 


Range — Miles 


Altitude 

feet 

Reliable operation 
(500 mv/m) 

Possible operation 
(200 mv/m) 

Dry4oil 

Moist soil 

Dry soil 

Moist soil 

1,000 

3* 

Ai 

6 

9 

5,000 

7h 

9 

13 

19 

10,000 

10 

12 

17 

25 

20,000 

13 

14 

23 

31 


14.3.3 Aircraft Modulating Unit 6 

The radio-controlled electric switch described in 
Section 14.3.2 operated from a tone-modulated signal 
of predetermined audio-frequency from a transmitter 
standard in bomber planes (SCR-522). A circuit was 
required to provide the tone modulation at the trans- 
mitter. Two models of this circuit were made and 
tested. They were not, however, put into production 
because of the lateness of their development. 

These two models had the same circuit, which dif- 
fered in the method employed to secure alignment 
with the audio-frequency to which the frequency was 
tuned. Model 1 was a stable fixed-frequency model, 
while Model 2 had its frequency continually varied 
over a range of ±85 c at the rate of 3 times per 
minute by means of a motor-driven condenser. The 
latter system was more flexible and did not require 
rigid adjustment of the set and the modulating unit. 
Either unit was portable, operated from dry batter- 
ies, and arranged to plug into the interphone system 
in place of one of the regular microphones. Function- 
ing depended upon adequate insulation of the unit 
from extreme cold. 


OPERATION AT 10 MEGACYCLES 


91 


14.4 OPERATION AT 10 MEGACYCLES 7 

It was determined that a practical switch small 
enough to fulfill tactical requirements could be de- 
veloped operating in a frequency range of 3 to 8 meg- 
acycles, provided by a standard CW ground trans- 
mitter used by OSS and based on the SCR-536 
Handy-Talky. A five-tube switch circuit using a 
39-in. vertical whip antenna was suggested which 
would meet most of the specified requirements in- 
cluding an operating life of 36 hours and a range of 
approximately 3 miles. The usual requirements of 
self-destruction upon exhaustion of the battery or 
upon attempted interference were included. 

The complete circuit comprised a converter, an in- 


termediate frequency amplifier, a detector, an audio- 
frequency amplifier, a limiter, and a rectifier. The 
circuit following the limiter was similar to the 1S5 
tube rectifier-amplifier and relay employed in the 
100 megacycle switch (Section 14.3.2). The frequency 
was accurately established by a crystal oscillator. 

Operation was provided by a field strength of 40 to 
150 microvolts per meter and for protection against 
false operation on interfering signals or noise, an 
audio-frequency selective circuit tuned to 100 c and 
preceded by the limiter to reduce the effect of vari- 
ation in signal strength was suggested. A time delay 
of 10 sec or more could be incorporated as an added 
safeguard. Figure 5 presents the significant part of 
the circuit of this device. 



3. l-c ADJUSTED TO RESONATE AT 100 CYCLES 

Figure 5. Circuit diagram of audio-frequency section of radio-controlled switch. 









































































PART III 


COMMUNICATION DEVICES 


In this part of the Summary Technical Report of 
Division 19 are described a number of developments 
which did not reach completion prior to the termina- 
tion of the division’s activities. They are all con- 
cerned with various types of secret communications 
over relatively short distances, ranging between a few 
feet and two or three hundred yards. The medium of 
communication was in some cases air and in others 
water. In every case, however, the object was to al- 
low individuals, presumably on reconnaissance mis- 
sions, to communicate with great security with each 
other either by telegraphy or by voice. The systems 
on which the devices were based were, therefore, 
those which rapidly attenuated with distance and 
which do not lend themselves to development to very 
great range. In Chapter 15 will be found the details of 
a system based on the induction field. Two devices 
are described, one the IFT, which was both a re- 
ceiver and transmitter, and the other an IFL, which 
was a transmitter alone. Operationally the IFT’s 
were considered useful for communication in jungle 
terrain by a reconnaissance patrol and for the loca- 
tion and direction of members of the party. The IFL 
was useful in the European theater as a homing de- 
vice on which the various members of a parachute 
stick could locate themselves after parachute landing. 
Both of the devices allowed this type of operation be- 


cause of their directional effect. They are the only 
ones of the devices described in this part which were 
produced in quantity and were of special interest to 
the Signal Corps and the Airborne Command. 

Chapter 16 describes various means of communi- 
cation through water. The operational use was of two 
kinds. In the first, communication across rivers or 
harbors or between craft and shore would be possible. 
In other applications communication between swim- 
mers or operators of underwater craft would be 
achieved and in this case could be either telegraphic 
or telephonic. A few models of the devices known as 
the UWT were produced and successfully demon- 
strated but the system was not fully explored. 

In Chapter 17 are described some miscellaneous 
devices based on supersonic communication and a 
microwave transmitter-receiver known as the MWT. 
These devices were even less perfectly developed and 
are recorded here to preserve the information ac- 
quired. In common with all the other parts of this 
volume, the contents of Part III are designed pri- 
marily for the individual operating alone or in a small 
party close to enemy lines and in a most clandestine 
manner. It is believed the devices will interest Army 
Ground Forces and the Signal Corps as well as the 
Navy and the Marine Corps. 


93 












































































































Chapter 15 

A SHORT RANGE INDUCTION-FIELD 
COMMUNICATING SYSTEM (IFT-IFL) 


15.1 INTRODUCTION 

In April 1943, several requests were submitted to 
Division 19 for short range secret signaling systems. 
The OSS and the Marine Corps described several sit- 
uations for which a communicating system, with a 
range of about 100 yd that would not be detectable 
by the enemy at distances greater than 200 yd, was 
desired. To meet this demand the induction-field 
transceiver (IFT) was developed for two-way com- 
munication at distances up to 125 yd and the induc- 
tion-field locator (IFL) was developed to emit auto- 
matically signals that could be received at distances 
up to 100 yd by means of an IFT. 

The induction field was used as a means of com- 
munication because the strength of the signal de- 
creases approximately as the cube of the distance 
from the transmitter. Thus a properly designed trans- 
mitter and receiver could be used at the desired 
range; at distances only a few yards beyond this de- 
sired range, the signal would be undetectable by 
enemy observers. The apparatus was developed to 
satisfy these criteria and to have minimum weight 
and volume consistent with an adequately rugged 
structure. 

The latest model of the IFT (Model B12), 1 con- 
structed in the laboratory in 1944 and produced in 
small quantities by a subcontractor in 1945, com- 
prised a metal case which could be attached to the 
belt of the operator, a coil which was strapped on his 
back, and an earphone which could be attached be- 
neath a helmet. The total weight of the transceiver 
was approximately 2.5 lb. 

The most recent model of the IFL (Model B8) la 
consisted of a single case into which the electronic 
equipment was assembled; the coil which produced 
the induction field was mounted around this equip- 
ment. The weight was approximately 2.5 lb and the 
size was 63^2 x 5 x 1% in. This instrument was also 
produced in small quantities early in 1945. 

Two or more operators, each carrying an IFT were 
able to communicate by coded signals at distances up 
to 125 yd. Because of the directional properties of the 
apparatus and the field which it produces, it was 
found possible for the operators of these devices to 
approach each other simply by listening to the coded 
signal from the other transmitter and by walking in 


such a manner that the signal strength increased. 
The IFL, put into operation by means of a switch on 
the device, transmitted a continuous signal for about 
16 hours. During this period an operator equipped 
with an IFT could locate the IFL if it were within 
100 yd of him by walking in the direction that gave 
rise to an increased signal. Beyond approximately 
200 yd, signals from the IFT and the IFL were in- 
audible on the receiving apparatus of the IFT and 
were thought to be inaudible by an enemy using any 
of the known scanning radio receivers. 

The following sections are devoted to a description 
of the IFT and IFL and to a description of tests of 
these devices. 


15.2 MODEL B12 IFT AND MODEL 
B8 IFL 

A coil carrying an alternating current sets up an 
electromagnetic field. The mathematical analysis of 
this field suggests that it be described as a combina- 
tion of two fields, an induction field and a radiation 
field. As the frequency of the current of the coil is in- 
creased, the distance from the transmitter at which 
the induction-field intensity and the radiation-field 
intensity are equal decreases ; this distance is equal to 
the wavelength (corresponding to the frequency of 
the current) divided by r. Thus, in the case of an 
alternating current of 50,000 c, the radiation field and 
the induction field are equal at a distance of approxi- 
mately 1,000 yd from the transmitter; and at higher 
frequencies, this distance is less. 

For a given current in the induction-field coil and 
for a given distance of separation of transmitter and 
receiver the received signal voltage increases linearly 
with the frequency. 

Therefore, if the induction field is to be used as a 
means of transmission, the frequency should be high 
in order to attain high sensitivity and the frequency 
should be low in order to achieve security. After ex- 
perimenting with induction-field transmitters and 
receivers over a range from 3,000 to 60,000 c, it was 
decided to choose a frequency of 50,000 c as a suitable 
compromise for the requirements in this problem. 
Frequencies less than 20,000 c have the advantage of 


f^E STOIGTEfi, ■ 


95 


96 


SHORT RANGE INDUCTION-FIELD COMMUNICATING SYSTEM 


increased security, but the apparatus for the low fre- 
quencies is excessively heavy and bulky. 

The major part of the development which led to 
the production of the Model B12 IFT was concerned 
with the problem of constructing from available com- 
ponents a compact, lightweight, transmitter and re- 
ceiver of 50,000 c induction-field signals. Many 
different types of tubes and different kinds of batter- 
ies were tried and extensive experiments were made 
to determine the optimum design of a coil for the 
transmission and reception of the signals. 

The resulting Model B12 IFT comprised a trans- 
mitting and receiving coil, a transmitter and receiver 
which together with batteries were included in an 
aluminum case, and an earphone. The aluminum 
case, which could be attached to a belt and supported 
in front of the operator, was 7 in. long, 43^ in. wide 
and 1 in. thick. The device was worn so that one of 
the ends in. by 1% 6 in. was upward, the case be- 
ing held flat against the body. In this upper end there 
were mounted a push button for sending coded sig- 
nals, and combination volume control and an on-off 
switch. Cable terminals for the induction-field coil 
and for the earphone were also mounted in this case. 
Within the case there were four vacuum tubes, bat- 
teries, and other circuit components. The batteries 
were so arranged that they could be easily removed 
and replaced without the use of special tools. One of 
the tubes was used as an oscillator for transmission 
and as a 50-kc amplifier for receiving. A second tube 
was used as a local oscillator to produce 47.5 kc per 
sec and as a converter. The output of this tube was 
put through a low-pass filter from which the audio- 
frequency signal was fed into a two-stage audio- 
frequency amplifier and then into the earphone. 

The induction-field coil consisted of 100 turns of 
number 27 wire, wound spider web fashion to reduce 
distributed capacitance. The coil was flat {YlYi x 
11% x %q in. thick). It was equipped with straps, 
so that it could be attached to the back of the oper- 
ator, and carried a cable, the plug of which was in- 
serted into the case of the transmitter-receiver. 

The Q of the coil and cable was found to be approx- 
imately 75. A photograph of the entire apparatus is 
shown in Figure 1, and the apparatus within the case 
is shown in Figure 2. 

In operation, two men equipped with the Model 
B12 IFT separated by a distance of about 100 yd 
turned on their devices and adjusted the volume con- 
trols to maximum. If operator A then pushed the 
transmit button of his device, the 50-kc oscillator 



Figure 1 . Model B12 IFT. (The electronic equip- 
ment and batteries are enclosed in the aluminum case 
at the right; at the bottom is the earphone; to the left 
is the induction -field coil which is strapped on the back 
of the operator. ) 

caused a current of this frequency to flow in the in- 
duction-field coil and thus set up an induction field 
surrounding him. Operator B would then hear a 
2,500 cycle signal unless his coil were turned at right 
angles to the plane of the transmitting coil. The sig- 
nal heard by operator B was caused by the voltage 
induced in his induction-field coil by the transmitted 
signal, the amplification of this signal by his first 
amplifier, the conversion of this signal to a 2,500 
cycle audio-frequency signal by his converter, the 
amplification of this audio-frequency signal by the 
two audio-frequency stages, and the audible signal 
thereby produced in his earphone. The maximum 
signal strength occurred when the coils were coaxial. 
Thus, operator B could determine the line-of-sight to 
operator A by turning until the signal was maximum. 
He could then walk straight forward; if the signal 
strength increased, he was approaching operator A; 
if the signal strength decreased, he was walking away 
from operator A. 

Figure 3 is the wiring diagram of the Model B12 
IFT. Note that the tubes are Raytheon Hearing Aid 
tubes. With each instrument a brief instruction 
manual 2 was issued. This instruction manual de- 
scribed not only how to operate the device but also 
how to adjust it for optimum sensitivity and how to 
replace batteries. 

The Model B8 IFL was a single tube transmitter 


TESTS OF THE IFT AND IFL 


97 



Figure 2. Chassis and battery holder removed from the case of Model B12 IFT. 



Figure 3. Circuit diagram of Model B12 IFT. 


built into a case 5 x 6^ x 1 % in. on a circuit de- 
signed to oscillate at 50 kc. The coil wound around 
the edge of the case and within its outside cover 
served, not only as the inductance of the oscillator, 
but also as the producer of the induction field. The 
operator of an IFT, within a range up to about 100 yd 
could hear the signal from the IFL and could ap- 
proach it in the same manner as that described above. 
Figure 4 is the wiring diagram of the Model B8 IFL. 
An instruction manual 3 for this device was issued 
with each such piece of apparatus. 


15.3 TESTS OF THE IFT AND IFL 

Extensive laboratory and field tests of the IFT and 
of the IFL were made in Philadelphia; in addition, 
several tests were conducted by various branches of 
the Services. Prior to these, early models of the IFT 
were subjected to a jungle test, 4 being exposed to 
tropical climate for several weeks. These tests showed 
that the apparatus as then designed was subject to 
fungus growth and deterioration so that it soon be- 
came inoperable. Subsequent models were designed 


DIS TRICTED | 




98 


SHORT RANGE INDUCTION-FIELD COMMUNICATING SYSTEM 


IS4 



Figure 4. Circuit diagram of Model B8 IFL. 


to minimize these effects; these later models, includ- 
ing the Model B12, were tropicalized, following 
Army recommendations for such procedures. The 
early models of the IFT tested in the jungle were 
found also to operate at a distance of only 50 yd 
through dense jungle undergrowth. This was the only 
report of a limitation of range due to vegetation. 
Subsequent tests of later models showed that the re- 
designed IFT operated satisfactorily at ranges of 
100 to 125 yd under similar circumstances. 

The Marine Corps tested several Model B4 IFT’s 
and found the range of that model to be about 75 yd. 
They also found that it was possible to communicate 
using one IFT within a tank and another instrument 
outside. 5 

The Model B12 IFT and the Model B8 IFL were 
submitted to the Army Signal Corps for test at the 
Camp Coles Signal Laboratory. 6 Their report indi- 
cated a reduction in range in an acoustically noisy 
location, but the character and causes of this acousti- 
cal noise were not described by the observer. These 
tests also showed that, using a Type HRO receiver 
equipped with a loop, the IFT and the IFL could be 
heard at about 100 yd but not at greater range. This 
result confirmed the design criterion that the signals 
from the IFT and the IFL would be secure from 
enemy scanning. The Signal Corps testers placed the 
receiving IFT about 20 ft from each of several radio 
transmitters and found no reduction in range, that is, 
no interference was produced by transmitters having 
several frequencies from 1 megacycle per sec to 240 
megacycles per sec and rated from a few watts to 
eight kw. As a result of these tests, the Signal Corps 
submitted a list of 19 specific recommendations for 
changing component parts of the B12 IFT in order to 
satisfy the specifications of the Armed Forces. The 
only basic design change was the suggestion that 
more audio-frequency amplification be provided to 


increase the output level when the IFT was used in 
a region where there was high-intensity ambient, 
acoustic noise. 

Four field tests and demonstrations of the B12 
IFT and the B8 IFL were organized in the European 
theater by an OSRD scientific advisor to the First 
Airborne Army, early in 1945. 7 

In these tests and demonstrations, the operation of 
the IFT and the IFL was explained to Army officers, 
and they were asked immediately to use the equip- 
ment for specific purposes. Thus, for example, an 
officer was told that an IFL was somewhere within 
75 yd of him, and he was asked to find it using an 
IFT. In spite of the complete novelty of the devices 
to the users, the tests were successful; the IFL was 
found, even when buildings and natural obstacles 
intervened between the initial position of the ob- 
server and the IFL. In one case, as an officer with an 
IFT approached to within 20 yd of the IFL and 
stopped to adjust his volume control, the IFL was 
moved quickly to a position behind the observer. 
Having adjusted his volume control he proceeded in 
the direction he had initially taken and found that 
the signal strength decreased. During the next few 
seconds he decided that the IFT was not operating 
properly and then turned and walked in a different 
direction. He quickly found the IFL in its new loca- 
tion. Even under the most difficult conditions, the 
IFL was located within ten minutes or less. During 
these tests also, two operators using IFT’s not only 
were able to find each other and to meet, but also ar- 
ranged coded signals so that one operator could di- 
rect the other to proceed forward, turn left, turn 
right, and so forth. On the basis of these tests, rush 
orders for 3,600 Model B12 IFT’s and 400 Model B8 
IFL’s were initiated. The first thousand items had 
been produced and shipped when the war in Europe 
ended. 

It was noted in tests performed by NDRC that the 
presence of metal near the induction-field coil modi- 
fied the frequency and decreased the range of com- 
munication. Thus, when an IFL was placed inside a 
steel railroad car, the range was about 50 yd when 
the IFL was near the center of the car, and was re- 
duced to about 15 yd when the instrument was placed 
flat against the steel wall of the car. Furthermore, the 
presence of the metal caused the frequency to be in- 
creased by approximately 5 per cent. On the other 
hand, an IFL placed in an automobile (sedan) travel- 
ling 40 mph was heard for a period of one second by 
observers with IFT’s 20 yd from the road along 


RESTRICT! 


CONCLUSION 


99 


which the car passed. Thus, although the presence of 
metal caused a decrease in range and an increase in 
frequency, it did not prevent the operation of the 
IFT or IFL. The Marine Corps tests mentioned 
above were consistent with these observations. 

Early in 1945, a representative of the developing 
contractor was loaned to the Office of Field Service, 
OSRD to take several devices to the Southwest Pa- 
cific area for demonstration. From March 1945 to the 
beginning of June 1945 he demonstrated the IFT and 
the IFL to units of the Sixth Army and others. In his 
reports submitted to the Office of Field Service, he 
recorded the descriptions of these demonstrations. 
The general conclusions which he reached by sum- 
marizing the comments submitted to him by officers 
who attended the demonstrations indicated the need 
in that area for devices with greater range than the 
range of the IFT and IFL. It was the concensus of 
opinion of these observers also that communication 
of this kind should be by voice rather than by code; 
that the range should be about 400 yd ; and that the 
need for security from enemy detection was not great. 

It would appear that the IFT and IFL were de- 
signed according to criteria which were more satis- 
factory for tactics in the European theater, than in 
the Pacific theater. No further development of the 
IFT and IFL along the lines suggested by the officers 
in the Pacific theater was attempted because of the 
late date. 

15.4 SUGGESTED CHANGES IN THE 
IFT AND IFL 

As a result of field demonstrations, numerous sug- 
gestions were made for changing the IFT and IFL. 
These are listed in detail in a separate report, 1 but 
several of them are presented below. 

It was recommended that the range be increased to 
200 or 250 yd. It is unlikely that this can be done 
without greatly increasing the weight and volume of 
the apparatus. The particular characteristic of the 


induction field which makes it useful for this purpose 
also makes it necessary to use very high-power equip- 
ment to achieve ranges greater than about 125 yd. 

It was suggested that the apparatus be redesigned 
to use voice transmission. This also would increase 
the weight of the equipment for the same range. 
Nevertheless, the use of voice is possible and could 
be investigated. 

It was suggested that the frequency be changed to 
100 kc. This frequency was initially avoided because 
it was thought to be within the range scanned by the 
enemy. No experiments were performed at this fre- 
quency, and theoretically, no great increase in range 
is to be expected at this frequency, but the experi- 
ments could easily be carried out if subsequent de- 
velopments required them. 

It was recommended that the IFT and IFL be de- 
signed to have several frequencies of transmission. 
This idea was tested by constructing two IFT’s 
which could be operated at 40, 50, or 60 kc per sec. 
The volume of the apparatus was increased and the 
weight was increased by about two pounds. The 
equipment operated satisfactorily at all three fre- 
quencies. This procedure enabled an operator to com- 
municate with each of three other operators who 
would not interfere with each other. 

15.5 CONCLUSION 

The use of the induction field for short-range com- 
munication was demonstrated to be an effective and 
useful method but the investigation was in no case 
carried to a complete conclusion since the devices 
were developed and produced for specific purposes. 
Thus there remains a field of investigation which 
might well bring out features of this mode of com- 
munication other than those which were included as 
the criteria for the development described herein. The 
work described here is believed to indicate clearly, 
however, that the induction field has possible value 
for military purposes. 


Chapter 16 


SHORT-RANGE COMMUNICATION 

CURRENTS 

16.1 INTRODUCTION 

It was requested that means be provided for inter- 
communication between ship and shore under con- 
ditions where security was extremely important. It 
was also suggested that a means of communication 
between a swimmer and a ship or another swimmer 
might be useful. Although no precise specifications 
were given, it was understood that the apparatus 
should have ranges varying from 200 to 2,500 yd, 
that the equipment should be as light in weight as 
possible, that it should operate satisfactorily at 
depths up to 100 ft, and that it should be as secure 
from enemy detection as possible. During the first 
stages of development, it was stated that code com- 
munication would be satisfactory, but it was later 
specified that transmission by voice would be more 
useful. Late in 1943 the suggestion was made that it 
might be possible to insert electrodes in sea water, to 
feed low-frequency currents into these electrodes, and 
to detect signals at some distance by another pair of 
electrodes inserted in the water; such a system was 
designated underwater telegraph or telephone [UWT]. 
By avoiding the use of radio signals, acoustic signals, 
infrared signals, and light, security was enhanced. 

The initial approach to the problem consisted of a 
theoretical analysis of the propagation of electric cur- 
rents in water and the design of electrodes for produc- 
ing such currents and for picking up signals. 1 This 
analysis showed, not only that it would be possible to 
devise apparatus to communicate by means of cur- 
rents in water, but also that the signals would have 
directional properties. Thus, such a method of com- 
munication might be useful for homing problems. For 
example, a ship might be able to find its way toward 
a signaling station on shore, and a swimmer might 
be able to find a ship on which a transmitter was 
mounted. 

Although some signaling of this kind had been 
done by Samuel F. B. Morse about 100 years ago, 
practically no references to recent work along these 
lines was found in the literature. Accordingly, a num- 
ber of models of transmitting and receiving equip- 
ment were constructed, tested, and then demon- 
strated to the Maritime Unit of OSS, the Navy, and 
groups informed of this development by the Office 
of Field Service, OSRD. These tests are described in 


BY MEANS OF LOW-FREQUENCY 
IN WATER 

a later section of this summary. During the course of 
this development, a sample of the British underwater 
craft called the Sleeping Beauty was obtained, and 
one model of the UWT was produced for installation 
in it. 

It should be emphasized that the specifications 
were never precise and were modified from time to 
time during the development. Thus, a number of 
models of the UWT were built and tested, but the 
investigation of this method of communication must 
be considered incomplete because the investigation 
was discontinued in June 1945 before precise speci- 
fications were determined and before the investiga- 
tion of possible designs was completed. 

16.2 THEORETICAL BASIS OF THE UWT 

The initial mathematical formulation 1 of the the- 
ory of the propagation of electric currents in water 
indicated the following important predictions, when 
two pairs of electrodes, one pair for transmission and 
one pair for reception, are placed in the same hori- 
zontal plane near the surface of sea water. The volt- 
age pickup at the receiver is directly proportional 
to the current between transmitting electrodes. The 
receiver signal varies directly with the distance of 
separation of the two transmitting electrodes. The re- 
ceiver signal varies directly with the distance of sepa- 
ration of the two receiving electrodes. The receiver 
signal voltage varies inversely as the cube of the dis- 
tance between the transmitter and receiver. The re- 
ceiver signal is maximum, if the transmitting elec- 
trodes determine a line which is parallel to the line 
determined by the receiving electrodes and if these 
two lines are perpendicular to the line between the 
transmitter and receiver. The receiver signal is the- 
oretically zero if the receiving and transmitting elec- 
trodes are colinear. This theoretical formulation sug- 
gests the possibility of determining in advance just 
how much current is desired for a particular range. 
These theoretical data also show that the signals have 
directional properties which may be useful for hom- 
ing. Also the inverse cube variation of receiver signals 
suggests that the system will be secure from enemy 
interference, even if he learns about the method and 
tries to detect the signals. 


100 


RF.STliKTKD \ 


EXPERIMENTAL MODELS OF THE UWT 


101 


It is clear that the minimum practicable value of 
received signal voltage will depend upon electrical 
noise in the receiver, noise picked up from the water, 
and the bandwidth of the receiver. Early experi- 
ments showed that the noise picked up from the 
water was relatively low level unless it was caused by 
apparatus such as the ignition systems of internal 
combustion engines.Thus it was unnecessary to pro- 
tect from noise, except when the equipment was to be 
used near such sources of noise as engines, motors 
with commutators, and so forth; in the latter cases, 
means were provided at the source of noise to mini- 
mize its effect on the UWT. The bandwidth must be 
about 300 cycles for code transmission and some- 
thing about 3,000 cycles for speech. The receiver 
noise was calculable. Subject to experimental con- 
firmation, which has been carried out, it was decided 
that there was a practical sensitivity limit of 10 -8 
volts for code and about 10~ 7 volts for voice. This 
specified the receiver sensitivity, that is, it deter- 
mined the receiver signal that would be useful. 

In order to determine the practical current that 
could be used in the transmitting apparatus, a theo- 
retical investigation of electrodes in sea water was 
conducted. It was found that the resistance between 
electrodes was about 1 ohm and that it was essen- 
tially independent of the distance of separation. 
These effects had a strong influence on the practi- 
cable distance of separation of the transmitting elec- 
trodes because the cables which conduct the current 
to the electrodes must have low resistances and were, 
therefore, relatively heavy and bulky. 

The theoretical computations concerning range, 
receiver sensitivity, and electrode resistance were 
confirmed by all of the experimental data using many 
different kinds of models. Thus, the theoretical basis 
of the UWT was found to be a dependable one. 

16.3 EXPERIMENTAL MODELS OF 
THE UWT 

Early models of the UWT are described very 
briefly in the following paragraphs. Following these 
brief descriptions there is a more detailed discussion 
of some of the later models, including the models 
which were installed in the Sleeping Beauty. 

16.3.1 UWT Models C-101 and C-102 

Model C-101 consisted of three 6SJ7 tubes which 
were resistance coupled and were tuned by a 1,500- 
cycle inverse-feedback network. For transmission, 


the tuned amplifier was adjusted to oscillate. Signals 
from the oscillator were fed into two hollow stainless- 
steel electrodes about two inches long inserted just 
below the surface of the water with a separation of 
about 100 ft. Signals were fed into this 5-ohm elec- 
trode system by means of a transformer chosen from 
standard items made by a manufacturer of trans- 
formers. The power supply consisted of a storage bat- 
tery and a vibrator system which produced 400 v. 
The total weight was about 100 lb and the power out- 
put of the Model C-101 was approximately 7 w. This 
model was for boat installation. Model C-102 weighed 
only 8 lb. It used a 120-volt battery power supply, a 
circuit somewhat like the Model C-101, and pro- 
duced about 0.2 w in a load resistance of 5 ohms. In 
tests conducted at Cape May, New Jersey, the vibra- 
tor power supply produced signals which interfered 
with reception on C-101, but signals from C-101 were 
heard at distances a little more than Y mile by 
means of C-102. 

16.3.2 UWT Models C-103 and C-104 

C-103 was an improved model somewhat like 
C-102, and C-104 was an improvement over C-101 . 
The power output of C-104 was 16 w. These two 
models with electrode spacings of 150 ft were oper- 
ated successfully at distances up to 1.5 miles in tests 
at Cape May in 1944. 

16.3.3 UWT Model C-201 

This model was a first trial at the problem of de- 
signing something that might be used by a swimmer. 
It was a complete receiver weighing about 2 lb. 

16.3.4 UWT Model C-206 

This model was an unsuccessful attempt to de- 
velop a pulse-generator to send out damped pulses 
having a natural frequency of about 1,000 c, and a 
duration of a few cycles. The signal could be heard at 
200 yd, but could not be heard at 400 yd and work on 
this approach to the problem was therefore discon- 
tinued. 

16.3.5 UWT Model C-301 

Model C-301 was a transmitter of 20 w output de- 
signed for minimum weight which was about 30 lb. 

All of the models mentioned above were built to in- 
vestigate experimentally the theoretical predictions 


102 


SHORT-RANGE COMMUNICATION 


presented in Section 16.2 and to test the practicabil- 
ity of the idea of using the UWT for short-range com- 
munication. From these two points of view, the ex- 
periments were entirely successful although further 
models had to be designed for specific applications. 
They are described in Section 16.4. 

16.4 LATER MODELS OF THE UWT 
16.4.1 UWT Model C-105 

This was a transceiver for code signals having a 
frequency of 2,500 c. Its range was 800 yd; its weight 
was 5 lb; and the life for continuous operation was 
15 hr. The power output was approximately 0.1 w, 
the apparatus was waterproofed and tropicalized, 
and the standard R-30U earphone was used as the 
receiver. The complete outfit with the cables coiled 
on a reel is shown in Figure 1. At the left end of this 



Figure 1 . Model C-105 UWT. 


picture some braided tubing can be seen. This was 
stretched over rubber tubing, and acted as the elec- 
trodes for the introduction of currents into the water. 
Each electrode was connected to the set by means of 
60 ft of cable. Thus the maximum electrode separa- 
tion was 120 ft, for which the range was 800 yd; for 
a separation of 60 ft, the range was 500 yd; for 30 ft, 
310 yd; and for 10 ft, 140 yd. The control panel, as 
shown in Figure 2, consisted of a send-receive switch, 
a key, and an on-off switch and volume control. The 
wiring diagram of this apparatus is shown in Figure 3. 
Note that there are two 1S5 tubes and one 1S4 tube. 
The transformers which were used to couple the 
transmitter to the water and to couple the water to 
the receiver were specially designed and wound on 
hypersil cores. This device was designed specifically 
to be taken to the Pacific theater by a representative 
of the developing contractor who was assigned to the 


Office of Field Service to demonstrate this equipment 
and other devices. 



Figure 2. The control panel of Model C-105 UWT. 

16.4.2 UWT Model C-500 

After the first speech transceiver, Model C-400, 
was constructed, Model C-500 was built for the pur- 
pose of providing a practicable unit, which could 
be used underwater by a swimmer or diver equipped 
with breathing mask and microphone, and which 
could, if necessary, withstand pressures correspond- 
ing to depths as great as 80 ft. The apparatus was 
waterproofed by assembling the major items into 
heavy metal containers sealed by rubber gaskets. 
Two of these sets were designed for installation in the 
Sleeping Beauty. Two others were portable models to 
be used for tests on auxiliary surface craft and they 
were not waterproofed. The effective range for the 
reception and transmission of these devices was 
250 yd when the electrodes were separated by a dis- 
tance of 25 ft. 

When the apparatus was installed in the Sleeping 
Beauty, one electrode was inserted near the bow and 


LATER MODELS OF THE UWT 


103 



Figure 4. Model C-500 UWT : apparatus removed from case. 


1.5V “■ 


— 67.5 V 

J- 


Figure 3. Circuit diagram of Model C-105 UWT. 


104 


SHORT-RANGE COMMUNICATION 



the other electrode was held out from the stern by 
means of a flexible pole. The batteries and electronic 
equipment were installed within the craft. The elec- 
tronic apparatus mounted within the submarine was 
enclosed in two cases, one for batteries, and the other 
for tubes and other components. These are shown in 
Figure 4. The circuit diagram of Model C-500 UWT 
is shown in Figure 5. The complete equipment, which 
was submersible, is shown in Figure 6. Note the 
waterproofed switch for changing from “transmit” to 
“receive” and the waterproofed earphone, both next 
to the mask. 

16.5 TESTS OF THE UWT 

Demonstrations of C-105 were carried out in the 
Pacific area (see Section 15.3) and, in addition to the 
tests at Cape May of the early models of the UWT, 
two test programs were undertaken at St. Peters- 
burg, Florida, under the auspices of OSS, and the 
Navy. 2 At the latter site, two portable battery units, 
attached to the backs of swimmers equipped with 
diving suits, operated satisfactorily at a distance of 


150 yd and a throat microphone was found to be 
preferable to a lip microphone. The waterproofed 
earphone was placed on the outside of the diving suit 
helmet, and performed satisfactorily. With the oper- 
ators separated by 250 yd, one on each side of a small 
island about 50 by 400 yd, communication was satis- 
factory, although it is probable that no greater range 
could have been used. 

One apparatus was installed in the Sleeping 
Beauty, one electrode being the propeller while the 
other electrode was a silver plated brass tube V/i in. 
in diameter, 2^ ft long, trailing at a distance of 
100 ft on an insulated cable. An identical set was in- 
stalled aboard an Army rescue boat [ARB] with 
electrodes off the bow and stern having a total sepa- 
ration of about 75 ft. With the ARB stationary, the 
Sleeping Beauty was operated on the surface in a 
circle with the ARB in the center at a radius of about 
150 yd. Null points were observed when the Sleeping 
Beauty and its electrodes were perpendicular to a line 
formed by the electrodes of the ARB. This is in ac- 
cord with theoretical predictions. The range test was 
carried out with the Sleeping Beauty running on the 




TESTS OF THE UWT 


105 



Figure 6. Complete equipment of Model C-500 UWT. 


surface directly astern the ARB. Thus, the electrodes 
were all in the same line which is the condition for 
maximum range. The signals were still satisfactory at 
a distance of 600 yd, and it was not desired that this 
range be extended for security reasons. Reception at 
the surface was good only when the Sleeping Beauty 
was stopped or running at slow speeds, apparently 
owing to the acoustic noise of the splash of water at 
high speeds. When the craft was submerged at depths 
up to 14 ft, reception was good no matter what the 
speed. It was noted during these tests that interfer- 
ence was produced by the ignition system of a JR 
Navy craft when it was within 20 yd of the receiver 
and also that the receiver on the ARB became in- 
operable when the motor of a motion picture camera 
was less than 30 ft from the ARB. However the inter- 
ference of the electric motor of the Sleeping Beauty 
was negligible throughout these tests. 

Suggestions ’ for modifications of the equipment 
based on these tests included the proposal that the 
transceiver and power supplies be placed in a single 
container, when used by a swimmer, and that the 
electrodes be in the form of cuffs, one on each wrist. 
Suggestions were also made to relocate the equipment 
used in the Sleeping Beauty to avoid interference 


with other facilities in the craft. Some of these modi- 
fications of the UWT were made, and subsequent 
tests were arranged as described below. 3 The chief 
purpose of these tests was to investigate the useful- 
ness of the bow electrode fitted over the craft and the 
rear electrode consisting of 2 ft of tinned copper braid 
mounted on a rubber tube trailing about 10 ft astern. 
The switchbox with all the controls was mounted on 
the steering column of the Sleeping Beauty. The 
second UWT was set up in a flat-bottom wooden 
boat with electrodes about 33 ft apart; this spacing 
being approximately equal to the electrode spacing of 
the Sleeping Beauty installation described above. A 
range of about 200 yd was attained throughout the 
tests, and mechanically, the new electrode system 
appeared to be satisfactory. These tests also showed 
that a sensitive earphone was required for satisfac- 
tory communication up to 250 yd, but that the limit 
was about 200 yd using a bone conduction receiver. 
The demonstrations of the UWT in the Southwest 
Pacific area confirmed the range prediction, and, in 
general, the apparatus performed as expected. How- 
ever, no specific uses for the UWT were suggested in 
that area, the observers desiring a longer range. They 
were quite concerned also about the necessity for a 



106 


SHORT-RANGE COMMUNICATION 


shore operator’s exposing himself along 100 ft of 
shoreline to place electrodes in the water. 

16.6 CONCLUSION 

It cannot be overemphasized that this development 
was carried out quickly near the end of the war with- 


out any precise designations of probable uses of the 
apparatus except for the Sleeping Beauty. The ex- 
perimental results confirmed the theoretical predic- 
tions and it is to be assumed that further experi- 
mental investigations might lead to the production of 
more satisfactory transceivers of relatively sharply 
defined, and short, range. 


Chapter 17 


A COMPACT MICROWAVE TRANSMITTER AND RECEIVER AND 
MISCELLANEOUS COMMUNICATING DEVICES 


17.1 INTRODUCTION (MWT) 

It was the purpose of this development to con- 
struct and test a low-power microwave transmitter 
and receiver 1 for short-range, line-of-sight, two-way 
communication by voice or code, having a range of 
approximately one-half mile and usable as a relay. 
As developed, it could be set up on a tripod or could 
be held in the hand and used as a long-range mega- 
phone. This microwave transmitter-receiver is ab- 
breviated MWT in the following. In it, the 723 A/B 
klystron operated at approximately 9,400 megacycles 
as an oscillator and a crystal detector was used for 
reception. 

17.2 TRANSMITTING AND RECEIVING 

CIRCUITS (MWT) 

As the repeller voltage of the klystron was varied, 
different modes of oscillation were produced. Thus, 
for example, as the repeller voltage was changed from 
90 v to 110 v, the power output increased to a maxi- 
mum for a repeller voltage of about 99 v and then de- 
creased again to zero. When the repeller voltage was 
adjusted approximately to the midpoint of one side of 
such a mode (in this case to about 106 v), the modu- 
lation could be applied to the circuit and a modulated 
9,400-mc signal was thereby produced. This was es- 
sentially amplitude modulation, although there was 
a small percentage of change in frequency. For code 
transmission, the modulating signal was an audio- 
frequency oscillator. 

The radiating system consisted of a rectangular 
horn. The receiving system comprised a half-wave- 
length antenna mounted in a parabolic reflector, and 
connected by means of a coaxial line to a crystal de- 
tector. Its output was fed to a two-stage audio-fre- 
quency amplifier having a gain of about 8,000. 

In order to adjust the repeller voltage for operation 
at the correct point on a mode as described above, the 
monitor crystal was mounted in the horn and con- 
nected to a microammeter. The repeller voltage was 
adjusted until maximum reading was obtained on the 
microammeter and the voltage was then adjusted un- 
til the microammeter reading was one-half the peak 
value. 


17.3 TWO MODELS OF THE MWT 

ModelF-101 receiver and ModelF-201 transmitter 
were initially constructed to test code operation, but 
later the transmitter was modified to permit modu- 
lation by voice, and a second receiver was built for 
voice reception. The transmitter produced a beam of 
about 20 degrees, a power output of 10 mw, and a 
range of approximately Yt mile using the modified 
F-101 receiver. The weight of the equipment was 
17 lb. 

A subsequent model of the MWT, designated 
Model F3, was a transmitter and receiver arranged 
to be packed for ease in carrying and mounting. 
There were three carrying cases. One contained the 
control unit and was 11 x lYi x in.; its weight 
was 10 lb; its power output was 10 mw. The second 
case weighed 34 lb and contained the batteries, the 
life of which was at least 15 operating hours. The 
third case contained the tripod and weighed 12 lb. 
Thus, the total weight was 56 lb. This device could 
be used as a transceiver for modulated code or for 
voice, and it could also be used as a relay station. 
The range for voice was about Yi mile, and as a relay 
station, the maximum safe range was Y mile. The 
apparatus, mounted on a tripod, is shown in Fig- 
ure 1. Note that the receiving parabola is mounted 
on top of the control box while the transmitting horn 
is within the control box. The microammeter on the 
face of the panel is for the adjustment of the repeller 
voltage as described above. Figure 2 shows the horn 
removed from one end of the case, and the modulator 
and receiver removed from the other end of the case. 
The circuit diagram of the Model F3 is shown in 
Figure 3. 

17.4 TESTS OF THE MWT 

As indicated above, relay operation over Y mile, 
telephone communication over Yi mile, and a range 
for code of 1Y miles were conservative ratings for 
the Model F3 of the MWT. This was shown by re- 
peated tests in the vicinity of Philadelphia. However, 
at a field test conducted in July 1945 near Washing- 
ton, D. C., a range of only 0.4 mile was achieved over 
an open field. It is believed that this slightly shorter 
range may have been caused by vegetation at a 


108 


MICROWAVE TRANSMITTER AND RECEIVER 



Figure 1 . Rear view of MWT, mounted on tripod. 


height of l ]/2 to 2 ft which decreased the effective 
height of each unit. 


17.5 CONCLUSION (MWT) 

The klystron used in this apparatus was not de- 
signed for battery operation and a tube designed for 
this specific purpose would be better. It is quite pos- 
sible also that considerably higher frequencies could 
be effectively used for short-range devices of this 
kind and that the weight and volume of the equip- 
ment could be reduced by using RM cells and multi- 
ple horn units. The possibilities of the system were 
not fully explored. 


17.6 MISCELLANEOUS COMMUNICAT- 
ING DEVICES — INTRODUCTION 

The following paragraphs comprise brief descrip- 
tions of several devices produced by the division’s 
contractor in addition to the devices described in 
Chapters 15, 16, and the first part of Chapter 17 of 
this volume. The equipment described briefly below 
is discussed in more detail in a single volume 2 and 
represents either branch roads from the main line of 
attack on the problem of short-range communication, 
or measuring equipment required in the course of 
this investigation. 


17.6.1 Short-Distance Signaling 
by Means of X Rays 
and Gamma Rays 

A portable Geiger-Muller counter was constructed 
in order to determine its usefulness as a receiver of 
signals from radium and from X rays. The device 
consisted of a box x 5 x 1J^ in. with a cylindri- 
cal extension 7% in. long and 1% in. in diameter; a 
battery, a vibrator, and vacuum tubes were mounted 
within the box, and a counter tube was mounted in 
the cylinder. The weight of the unit was 27 oz. Sig- 
nals were heard in earphones connected to the device. 
The background counting rate was about 25 counts 
per min but this rate was caused to double (50 counts 
per min) by gamma rays from radium or X rays at 
the following ranges: for 0.6 mg of radium, the range 
was 30 ft; for dental X-ray apparatus operating at 
60 kvp 5 ma, the range was 500 ft. Since the trans- 
mitting apparatus was expensive, dangerous, and, in 
the case of X rays, heavy, this method of short-range 
communication was not investigated further. 


MISCELLANEOUS COMMUNICATING DEVICES 


109 



Figure 2. Partially disassembled view of MWT showing (left) the horn unit, ( center ) the case, and (right) the modulators 
(single tube) chassis, receiver (3-tube) chassis, and plug chassis. 


17.6.2 An Ultrasonic Whistle and 
Other Acoustic Devices 

An ultrasonic whistle of the Galton type was con- 
structed of metal, and subsequent models were made 
of lucite. Fixed-frequency whistles from 15 kc per sec 
to 30 kc per sec were built. The power output varied 
from 50 to 100 mw, and the efficiencies were between 
2]/2 and 5 per cent when blown by an operator with 
normal healthy lungs and chest. Signals from such 
whistles could be heard with a suitable microphone 
(see Section 17.9), a small receiver using microtubes, 
and an earphone. The receiving equipment would 
weigh about 2 lb. 

A generator of audio frequencies called the hooter 
was investigated in conjunction with a study of can- 
ister locators (see Chapter 18). Figure 4 shows two 
models of the ultrasonic whistle and two models of 
the hooter. The hooters could not be blown effec- 
tively by mouth since they operated only at very 
high pressures. The hooter was also used as a source 
of underwater sound at frequencies of about 3,000 c 
and tests indicated that it might be possible to con- 
struct a device of this kind which would have a range 
of about one mile. 


17.6.3 Condenser-Microphone for 

Ultrasonic Measurements 

In order to investigate the acoustic and ultra- 
sonic sources described, it was necessary to set up 
acoustic measuring devices. In the course of this 
work, a condenser-microphone was designed, con- 
structed, and tested. The complete device with a 
mounting cylinder containing a pre-amplifier is 
shown in Figure 5. 

17.6.4 Free-Field Room for 
H F Measurements 

In order to carry out the tests described in the 
above paragraphs, and to calibrate the microphone 
described above, a small room was designed and 
built to have free-held characteristics at frequencies 
above 500 c. This room was x 9 x 11 ft and was 
lined throughout with blankets of glass wool folded 
into herringbone pattern (Figure 6). It was found 
that the inverse square law at frequencies above 
2,000 c held for 9 ft along the diagonal of the room. 
Thus, for frequencies above 500 c, a quite small and 
inexpensive free-held room could be constructed. 


110 


MICROWAVE TRANSMITTER AND RECEIVER 



Figure 3. Circuit diagram of MWT Model F3. 



MISCELLANEOUS COMMUNICATING DEVICES 


111 



f— -r— H 

Figure 4. (Top) production models of ultrasonic 
whistle (left) brass, (right), lucite,' (bottom) hooters 
(left) push-pull, (right) single-ended. 



Figure 5. Condenser microphone with pre-amplifier 
mounted in carrying case. 



Figure 6. 


Interior view of field-free room showing construction of walls and arrangement of measuring equipment. 






































































- 


















































































































PART IV 


FIELD ACCESSORIES 


In this part of the Summary Technical Report of 
Division 19 is gathered together a miscellaneous 
group of devices which have been called field acces- 
sories because they would be of value to specialty 
groups operating on special missions but, would not 
by their absence, prejudice the success of such groups. 
It was the opinion of personnel in Division 19 that, 
by the use of the developed equipment described in 
the following chapters, operations would in a limited 
way have been made easier. 

Probably the device described which would have 
the greatest usefulness to the largest number would 
be the military adhesive given in Chapter 19. By this 
development, a means was provided demolition 
crews for the rapid and secure affixing of explosive 
charges to targets, regardless of the surface condi- 
tions of those targets. 

Of interest to the Airborne Command was the 
equipment described in Chapter 18 which would per- 
mit the more rapid and certain location of supplies 
dropped by air in difficult country. Chapter 21 should 
also interest airborne personnel, especially those em- 
barking on individual missions designed to gather 
intelligence and elude detection. 


In Chapter 23, dealing with the quieting of out- 
board motors, reference is made to work which suc- 
cessfully reduced the sound level of standardly issued 
motors by a percentage sufficient to allow the secret 
use of craft propelled by these motors close to enemy 
observation. For individuals, who might make land- 
ings by these means, a compact and reliable water 
purifier capable of one month’s operation under the 
worst field conditions is described in Chapter 22. 

Finally, in Chapter 20 are listed a number of simple 
but certain ways in which an Intelligence officer, 
operating clandestinely in enemy territory, could 
rapidly dispose of confidential documents which 
should not be allowed to fall into enemy hands. 

The whole group of devices is therefore, somewhat 
tied together and is probably even more specialized 
than the developments described in other parts of the 
STR. The groups in the Services to whom these de- 
vices should be of interest would include the Corps 
of Engineers, the Airborne Command, the Army 
Ground Forces, Army Intelligence, and the Surgeon 
General’s Office, as well as comparable Bureaus in 
the Navy. 


113 






























































































. 

















































































































































Chapter 18 

PARACHUTE LOCATING DEVICES 


18.1 INTRODUCTION 2 

The supply of ground troops, by the dropping of 
stores from aircraft, became a familiar operation in 
World War II. During the tremendous movements 
in Western Europe, this dropping was on such a scale 
that it could be conducted en masse in the daytime 
with good percentage of recovery of supplies. Such 
was, however, not the case in isolated operations of a 
very small nature. Numerous field reports were read 
from time to time which showed that small parties on 
scouting or reconnaissance work became detached 
from their main source of supply and required sup- 
port by aerial dropping of stores. Similar supply to 
aircraft forced down in unapproachable regions was 
a problem. 

Since these operations generally were conducted 
close to enemy lines by small groups who would be 
vulnerable to attack, dropping was preferably done 
at night when enemy detection would be at a mini- 
mum. This posed the problem of supplying the re- 
ception group on the ground with simple means for 
the location of the parachute and its accompanying 
load. Darkness was a severe handicap but was not 
less serious than difficulties of terrain, vegetation, 
and the inevitable wide dispersal of containers which 
resulted even in the most careful supply operation. 
For example, under favorable circumstances a sup- 
plying aircraft dropping both metal containers and 
bundles at stalling speed (130 to 140 mph) at heights 
of about 400 ft produced a total spread among 18 con- 
tainers of somewhere between 40 and 120 yd. If this 
good performance were even equaled under adverse 
field conditions, including darkness, thick jungle foli- 
age, and rough terrain, it is easy to see that many in- 
valuable containers would have been lost. 

The problem was certainly an urgent one, but it 
was considerably complicated by the feeling among 
the potential users that no aid to location should be 
used which would alert the enemy. This would re- 
quire that those on the ground be equipped with 
some manner of receiving or detecting apparatus un- 
available to the enemy, and, in view of the fact that 
the groups to be supplied might not always be pre- 
pared for such supply, it seemed logical to division 
personnel that this requirement should be altered to 
allow use of the senses, but to place safety in a non- 
suspicious type of signal. This chapter describes a 


device based on this hypothesis and utilizing the 
sounds of a special whistle. 

18.2 BASES FOR DESIGN 1 

Theoretically a great many physical phenomena 
could be used for a parachute locating device. Among 
the less likely would be odors, smoke, phosphorescent 
paint, fluorescent chemical reactions, and so forth. 
The more likely would include various methods of 
radio detection, supersonic signaling, infrared or 
visible light, and audible signaling. All of these were 
evaluated before a choice was made. 

Radio was considered to have a number of impor- 
tant advantages, such as control of the frequency of 
transmission, security from the enemy, and inde- 
pendency of the type of terrain. However, it would be 
difficult to limit a radio transmitter to a short range, 
and the problem of designing a cheap, expendable, 
and robust apparatus seemed difficult. Presumably a 
spark generator would have been more sturdy than 
a vacuum tube oscillator, but the advantage of se- 
curity would have been lost by the large spectrum 
emitted. Signaling by means of the electromagnetic 
induction field (IFT, see Chapter 15) has already 
been noted as a possible solution to the problem. 
Supersonic signaling would be ideal, if the receiving 
apparatus were not of great complexity. Unfortu- 
nately, attempts to utilize this system appeared un- 
promising especially because of the line of sight 
limitation. 

Visible signals were already in use. 4 They were, 
however, visible at night at very great distances with 
loss of security and were, of course, very unsatis- 
factory in high grass, or underbrush. 5 Moreover, all 
the methods mentioned above required batteries, in- 
troducing the problem of functioning after exposure 
to the very low temperatures encountered in aircraft 
operation. 

There remained radioactive emmanation, which 
was quickly shown to be impractical on economic and 
medical grounds, and audible signaling. The latter 
was chosen, since it required no additional receiving 
apparatus beyond the human ear. It could be simply 
produced without the use of batteries or complicated 
electric systems in a sturdy form capable of very 
rough handling and could be selected in frequency so 




115 


116 


PARACHUTE LOCATING DEVICES 


as to be rapidly attenuated beyond the desired dis- 
tance of operation. The nature of the sound could 
also be selected to pass unnoticed, unless the hearer 
were listening carefully for the particular tone. This 
seemed to eliminate bells 5 from consideration, and 
the work of the division was therefore directed toward 
the development of a gas-blown whistle. 

18.3 WHISTLE MODEL 1 

18.3.1 Choice of Frequency 

From the point of view of security, the choice of 
pitch should be such that the attention of the enemy 
would not be greatly attracted. This indicated a fre- 
quency about 1,000 cycles, since this was likely to be 
masked by local noises such as those produced by 
mechanized equipment or jungle animals. On the 
other hand, the attenuation of sound in air increases 
by the inverse square law as the frequency is in- 
creased. This led to the belief that any frequency be- 
tween 2,500 and 4,000 cycles would be satisfactory 
and to the ultimate choice of 3,000 c in a pure tone. 
It was felt that the latter would be easily detected by 
those who were listening for the sound, but likely to 
escape the attention of unsuspecting personnel. 

18.3.2 Choice of Whistle 

After the construction of several different models 
based on different principles already revealed in the 
published scientific literature, a very simple whistle 
was accepted as best for the purpose. This resembled 
the large steam-operated whistles used on boats. Air 
was ejected from an annular orifice toward a resonant 
cylinder placed a short distance away. The efficiency 
of this design was good, the tone emitted relatively 
free from harmonics, and the mechanical tolerances 
involved in mass production easily met. 

18.3.3 Gas Supply 

The above whistle required for good operation a 
supply of compressed gas at a pressure of about 25 lb 
per sq in. Simple connection of the whistle to a stor- 
age tank of gas at this pressure would have been suit- 
able, except for the tremendous volume of gas which 
would have been required to give any reasonable op- 
erating life. It therefore appeared necessary to pro- 
vide a two-stage gas supply with a reservoir of gas 
under very high pressure continually supplying a 
larger reservoir of gas maintained at the proper oper- 
ating pressure. 


Two designs were built and a number of prototype 
models. In one design (the so-called Kidde Model) 
the gas was stored in the high pressure tank at 1,800 
lb per sq in. and by a valve system released to the 
lower tank, building up a pressure there of about 
25 lb per sq in. In the second design (the so-called 
Mine Safety Appliance Model) the original high 
pressure cylinder had gas compressed at about 500 lb 
per sq in. and operated when the low pressure tank 
reached 15 lb per sq in. Schematic drawings of these 
two designs constitute Figure 1. 



RELEASE MECHANISM VALVE 


AUXILIARY 


STORAGE TANK PRESSURE VOLUME 



R TIME DELAY 

D VALVE 

Figure 1 . Schematic diagrams: Kidde and Mine 

Safety Appliance Models. 

18.3.4 Intermittent Operation 

Preliminary tests indicated that a listener could 
more accurately determine the direction of an oper- 
ating whistle, if the operation were intermittent 
rather than continuous. It was found also that this 
type of sound was less likely to arouse suspicion. 
Moreover, an intermittent signal would require less 
energy for operation and, hence, give a longer time 
of service. Therefore the device was designed to give 
intermittent whistling with the average blast close to 
2 sec in duration and the intervening silent periods 
between 4 and 10 sec. 

18.3.5 Alternative Designs 

Reference to Figure 1 indicates the schematic de- 
sign for the Kidde Model, which was the device put 
into semi-production and later into somewhat larger 
production by OSS. Figure 2 is an external view of 
one of these models. 



PERFORMANCE 


117 



Figure 2. Canister locator — Kidde Model. 

In this model gas stored in the pressure tank at 
1,800 lb per sq in. was released when an external cord 
was pulled, opening a ball check valve. The released 
gas flowed into a regulated pressure chamber against 
a regulator diaphragm which was adjusted to main- 
tain a pressure of approximately 50 lb per sq in. After 
leaving this step-down chamber, the gas flowed 
through a small leak into a 1-quart volume (the so- 
called low pressure chamber) and there built up the 
pressure to about 25 lb per sq in. For the first oper- 
ation this required a period of about 20 sec, which 
was considered sufficient for the parachute and its 
load to have reached the ground. Thus operation of 
the whistle began only after the devices had landed, 
although it was initiated by the pulling of the external 
cord when the package left the plane. When the low 
pressure chamber reached the necessary value, a dia- 
phragm valve opened and allowed the gas to flow into 
the whistle, which was attached to it by a short piece 
of rubber tubing. The gas flow into the whistle was 
more rapid than that into the chamber, and hence 
the pressure decreased to about 22 lb per sq in., when 
the valve reseated and the whistle was shut off. At 
this instant, the pressure began to build up again and 
the cycle repeated itself. Once located by a receiver, 


the device could be stopped immediately by removal 
of the rubber connecting line between the low pres- 
sure tank and the whistle. 

The so-called Mine Safety Appliance Model 8 had 
an adjustable flow valve replacing the fixed leak into 
the low pressure chamber. In this way, the period be- 
tween signals could be controlled. In addition, there 
was a delay valve which in combination was the dia- 
phragm assembly allowed for an independently ad- 
justable initiation time delay. This feature answered 
criticism from the Services that the initial 20-sec 
period was too brief. The remainder of the operation 
was essentially the same as described above. 

Both devices were capable of being recharged from 
a cylinder of compressed gas but were considered by 
the designers to be expendable items which would 
have justified their cost by locating the unavailable 
loads they accompanied. It appeared likely that the 
second design would be somewhat cheaper in mass 
production because of less expensive valving. On the 
other hand, the second design illustrated in Figure 3 
was of a less convenient shape because of the neces- 
sity of having the high pressure cylinder in the form 
of a doughnut. The Kidde Model measured 12J^ x 
5% x V /2 in. and weighed approximately 7 lb. 



Figure 3. Canister locator — Mine Safety Appliance 
Model. 

18.4 PERFORMANCE 3 4 5 

Only the Kidde Model was extensively tested, 
from which it appeared to be extremely robust and 


118 


PARACHUTE LOCATING DEVICES 


reliable in its operation, being affected adversely only 
by very low temperature. This defect was a function 
of the valve seats, which when made of lead gave 
severe pressure losses during cold storage. The diffi- 
culty was nearly entirely corrected when these were 
replaced by rubber. Typical performance data are 
given in Table l. 6 This performance was affected by 


Table 1 . Typical performance data on Kidde Model. 


Chamber 

pressure 

Initial 

delay 

period 

Blast 

period 

Silent 

period 

Total 

functioning 

time 

1600 psi 

27 sec 

1.9 sec 

10.2 sec 

28 min 

1980 psi 

31 sec 

2.0 sec 

9.7 sec 

26 min 

1850 psi 

11 sec 

2.7 sec 

10.4 sec 

28 min 


exposure to high temperatures (120 F) to give a much 
shorter initiation delay period (4 sec) and an in- 
creased total functioning time (35 min). 

The range at which detection of the locating device 
was assured was greatly affected by the terrain, the 
ambient noise level, and the wind direction. In a com- 
parative test of this device with bell and light de- 
vices, it appeared to be largely a matter of personal 
preference which type seemed most secure. There 
was no doubt that the range of the whistling device 
was considerably greater, thus bell devices gave a 
range of 100 to 200 yd, lights gave an identical range, 
and whistles a range of 400 to 700 yd under the same 
conditions. 5 The above figures were obtained on a 
quiet day. On windy days, the effective range was 
often decreased to less than 300 yd, and it appeared 
as expected that this was further affected by the pres- 
ence of external noises and by the type of terrain and 
vegetation. If the latter, in an individual operation, 
were not important because of fortunate circum- 
stances, then undoubtedly lights would be more ef- 
fective for locating devices, but, in general, where no 
control was possible over the choice of locale, lights 
seemed much inferior, since they were easily masked 
by accident. The manner in which a whistle locator 
would be used is shown in Figure 4. 

When used in this way, the whistle in actual tests 
out-performed comparable light devices and failed to 


function only in the rare instances where the bundle 
lay over the locator, muzzling it. 

In summation, it may be said that a choice be- 
tween individual locators appeared to be entirely a 
subjective matter. To those in Division 19 connected 
with the work, the whistle device seemed preferable 
to either the bell device used by certain British groups 
or light device used by the Airborne Command. A 
really conclusive comparative test of the three was 
never undertaken. The value of some such locator 
was, however, apparent. 




Figure 4. Canister locator attached to Airborne 
Command bundle. 


Chapter 19 

MILITARY ADHESIVES 


19.1 INTRODUCTION 

The standard demolition kits used by Army 
Ground Forces and Corps of Engineer squads con- 
tained equipment by which sappers could affix their 
charges to selected targets. The means employed 
were, in general, improvisations featuring particularly 
tape, wire, and wooden props, by which intimate con- 
tact between the charge and the target was hoped for 
but not always secured. The demolitions contem- 
plated were performed on a great variety of surfaces 
such as steel, dressed or rough wood, machinery, and 
concrete, and the operations against these surfaces 
took place both during actual combat and behind the 
lines, so that the initiation of the explosive charges 
was frequently accomplished by either time delay 
Pencils (see Chapter 9) or by electrical blasting caps. 
For all such operations, there was a field requirement 
for an adhesive material, which, in the ideal case, 
could be smeared on the surface of the explosive 
charge and would affix that charge to the target for an 
indefinite period regardless of the condition of the 
target’s surface. This meant the development of an 
adhesive retaining its properties over an extreme 
temperature range of 0 to 140 F and on all the above 
surfaces when dry, wet, oily, or dirty. 

At the suggestion of OSS and the British liaison 
officers assigned to it, Division 19 was engaged in 
this development when liaison was established with 
the Corps of Engineers and later with the Army 
Ground Forces. The outcome of the cooperative 
effort was the development of two different materi- 
als, RD-43-141 and RD-44-41, differing slightly from 
each other in their behavior toward water but essen- 
tially meeting the above-described field requirements. 
Procurement of the former of these was undertaken 
by the Engineers in quantity. The product thereby 
obtained was superior to competing British develop- 
ments and vastly superior to a similar composition 
issued by the German army. 

19.2 THEORETICAL CONSIDERATIONS 1 

Following tests on 25 different types of commer- 
cially available adhesives, the division’s contractor 
arrived at compositions made up essentially of three 
materials: a base, a filler, and a plasticizer. These 
three were properly compounded to meet the field re- 
quirements by a balance of their rheological proper- 


ties: tack, yield value, and workability. Tack was de- 
fined as pull resistance and involved liquid flow or 
viscosity. Yield value was defined as the resistance 
which the composition offered to flow when subjected 
to a given stress. (This was generally applied in shear, 
rather than tension, because the former was a more 
difficult condition.) Workability was an estimate of 
the plasticity of the material and its handling proper- 
ties under a variety of temperature conditions. Most 
of the commercial materials failed in their perform- 
ance because these three properties were not properly 
balanced. The theory can be illustrated by Figure 1. 



Figure 1 . Theoretical behavior of adhesives under 
applied stress. 


Curves A and B in the above diagram represent 
pure liquids, true solutions, or dilute suspensions, 
where the particles are loosely related to each other 
and there is no interlocking or overcrowding. Such 
materials, regardless of their tack, would not support 
any load in shear because an infinitesimally s'mall 
load would start their flow. In other words, their 
yield value would be zero. The viscosity of material 
B, however, would be greater than that of material A , 
since a greater stress would be required to produce 
the same rate of flow ( y vs x). Curves C and D repre- 
sent materials which have a positive yield value. This 
is presumed to be because of an interlocking arrange- 
ment of the molecules or particles which must be 
overcome before the material will flow. Curves C and 
D would be true theoretical examples of this type. 
Both materials C and D have the same yield value 
but differ in other respects, C being less viscous than 
D and therefore having greater workability. D on the 
other hand, because of its greater viscosity, would 
resist sudden shock to a greater degree. 

Based on these considerations, and particularly 
with the hope of retaining tack in the presence of 


119 


120 


MILITARY ADHESIVES 


water, a number of mixtures containing rubber, rosin, 
vinyl, alkyd, phenolic, and urea resins were tested. 
Of these, only a mixture based on limed rosin or ester 
gum retained sufficiently its original tack when tested 
under water. This was shown to an enhanced degree 
when the gum was plasticized with Flexol Plasticizer 
3GH. In the interests of workability, this mixture re- 
quired the addition of a filler, and a study of the pos- 
sibilities indicated a preference for asbestos. Thus on 
the basis of theory, a composition likely to meet the 
field requirement was discovered. 

19.3 COMPOSITION RD-43-141 1 

19.3.1 Choice of Plasticizer 

Study of a number of plasticizers combined with 
rosin was made to determine the variations in vis- 
cosity with weight proportion, and the variations in 
viscosity with molecular weight. It was evident from 
this study that tack was primarily concerned with the 
viscosity range and was independent of the groups 
present in the plasticizer, the latter being important 
only in determining water solubility of the compo- 
sition. In Figure 2 the performance of the best of 
these plasticizers with both ester gum (A) and rosin 
(B) is recorded. 

i 

o 

z 



VISCOSITY OF ADHESIVE (NO FILLER PRESENT ) 


Figure 2. Viscosity-adhesion curves. 

Curve C represents concentrations of phenolic 
resin giving a composition too stiff for application. 

From Figure 2, it was apparent that ester gum 
was preferable to rosin with the best plasticizer 
found (triethylene glycol di-2-ethylbutyrate = 3GH). 


The latter plasticizer was, moreover, favorable be- 
cause of its extremely low vapor pressure, even at 
temperatures as high as 200 F. The load-carrying 
capacity of mixtures of ester gum and 3GH appeared 
to increase with increase in viscosity. This, however, 
was limited practically by the increasing stiffness and 
was sensitive to percentage composition; thus vari- 
ation of the amount of ester gum between 83 and 
90 per cent caused a change in viscosity from 1,290 
to 232,000 KV. At the same time, it was noted that 
viscous liquids without fillers would support no load 
for more than a few minutes without gradual yield, 
whereas the same mixtures mixed with fillers could 
support loads indefinitely. 

19.3.2 Choice of Filler 

Having shown the necessity for a third component 
in the mixture, a variety of fillers was studied, chief 
of them being carbon black and asbestos floats. The 
former in all compositions displayed an isothermal 
transformation upon agitation and rest, a phenome- 
non known as thixotropy, and thus, although such 
carbon-filled adhesive had excellent workability, the 
unpredictability of their behavior ruled them out of 
further consideration. 

Asbestos floats, on the other hand, appeared well- 
suited and it remained only to determine the opti- 
mum amount to add to the ester gum plasticized 
mixture. Trials indicated that addition of 43 per cent 
of floats to 57 per cent of the mixture gave a compo- 
sition having satisfactory workability and the maxi- 
mum shear strength (180 grams psi). Alteration of 
this mixture by addition to the asbestos of wood flour, 
cotton linters, and so forth, produced no improve- 
ment. 

Having come close to the final composition, the 
effects of variation in filler concentration and of vari- 
ation in ester gum concentration were studied. Thus 
the final optimum composition was arrived at and 
was designated as RD-43-141. It was as follows: 
30.4 parts of limed rosin (ester gum), 29.2 parts of 
3GH plasticizer, and 40.4 parts of asbestos floats. 
This material was found to have good workability 
from 30 to 125 F and a yield value over this temper- 
ature range of between 200 and 90 psi on dry steel 
surfaces. 

19.3.3 Choice of Base 

As has already been said, early experiments indi- 
cated that ester gum was preferable to other mate- 


PERFORMANCE 


121 


rials. Having found what appeared to be the optimum 
composition of this material with plasticizer and 
filler, a search was made for other bases which, with 
these materials, might perform more satisfactorily. 
None was found, and accordingly RD-43-141 was 
recommended to the Services as the best material 
which could be developed. 

19.4 COMPOSITION RD-44-41 1 

Trials of the composition RD-43-141 gave good re- 
sults on most surfaces except wet concrete. 3 ’ 6 At 
Service request a further attempt was made to im- 
prove the adhesive mixture with regard to this point. 
This led to the incorporation of a fourth component, 
Bentonite, a silicate mineral having the property of 
swelling remarkably with water. It was believed that, 
if this material were part of the adhesive composition, 
its affinity for water and resultant swelling would 
cause the adhesive to penetrate into the rough con- 
crete surface and provide a firm bond. Several com- 
positions having added Bentonite were tested with 
gratifying results. 

Eventually a mixture known as RD-44-41 was pre- 
pared in which the four components were apparently 
at the optimum concentrations as follows: 22.8 parts 
of limed rosin, 37.2 parts of 3GH, 21.0 parts of as- 
bestos floats, and 30.0 parts of Bentonite. This mix- 
ture retained all the properties of RD-43-141 with 
regard to workability, tack, and yield value at tem- 
peratures between 40 and 125 F. A sacrifice had 
therefore been made in the low temperature range at 
which the material was suitable for use. On the other 
hand, excellent performance on wet targets, particu- 
larly with concrete, resulted. A choice between these 
properties was made by the Corps of Engineers, OSS, 
and the Army Ground Forces in favor of RD-43-141 
and procurement of that was undertaken. 

19.5 MANUFACTURE 1 

All the materials used were readily available and 
inexpensive. Specifications for them were given to the 
procuring Services, as well as tests which would as- 
sure a uniform and satisfactory product. The appara- 
tus used for milling and kneading the adhesive was 
standard equipment, and the packaging of it in flat 
tin cans presented no difficulty. The chief require- 
ment was that the adhesive strength under controlled 
conditions should be, at least, a minimum value and 
that the workability on the other hand should also be 


satisfactory. A balance had to be maintained between 
these two competing qualities. 

19.6 PERFORMANCE 

The development work required the use of stand- 
ard test conditions, and these were selected as the 
load supported in shear by a given area of adhesive 
adhering to a standardized steel plate at a controlled 
temperature. 1, 4 Such laboratory procedures, of 
course, did not approach field conditions, and the 
work of the contractor was greatly facilitated by fre- 
quent and exhaustive trials of this kind performed by 
the potential users. 2 - 3 - 5 - 6 In these trials, the stand- 
ard demolition blocks used by the Engineers, the 
British, and the Army Ground Forces were applied 
with adhesive to a great variety of targets under 
winter and summer conditions, with and without oil, 
water, or dirt present. 

A summation of these tests was sufficiently con- 
vincing to the Services to warrant adoption of the 
item. They may be qualitatively summarized as fol- 
lows: against all types of dry, clean targets over the 
whole temperature range at which the adhesive com- 
positions were workable, the application of 34 to 
34-in. adhesive to a standard block of explosive would 
hold that block in place on a vertical or inclined sur- 
face for an indefinite period (over 24 hours). Similar 
trials against the same surfaces thoroughly soaked 
with water gave less satisfactory results, but only in 
the case of wet concrete was the loss in efficiency seri- 
ous, and this was rectified by the development of the 
composition RD-44-41. On the same surfaces coated 
with oil, results were comparable with those obtained 
on dry surfaces, inasmuch as the oil and the plasti- 
cized mixture were entirely compatible with each 
other. On the same surfaces heavily coated with dust 
or dirt, serious failure could be expected, but could 
hardly be laid to the adhesive for while this material 
was able to adhere adequately to the dirt surfaces, the 
latter had no strength of adhesion to the underlying 
target. This indicated that, in field usage, it would be 
necessary to prepare very dirty surfaces by a prelim- 
inary rub. This deficiency was not felt serious and 
could be easily overcome by adequate training. 

In conclusion, it seems to the writer that, barring 
temperature range, a very satisfactory solution was 
produced to a very difficult problem, and it is be- 
lieved that the use of these military adhesives would 
make the task of demolition crews considerably easier 
in the field. 


Chapter 20 

AIDS TO INTELLIGENCE 


20.1 INTRODUCTION 

Men on special missions either carrying or gather- 
ing Intelligence are in danger of interception, with 
consequent loss of vital information or revealment to 
the enemy of matters of interest to him. Persons en- 
gaged in such hazardous undertakings would there- 
fore be greatly assisted by devices which would allow 
the complete, instantaneous, and certain destruction 
of documents in their possession. 

Division 19 at the request of OSS evolved several 
developments, which should be of continuing interest 
to Intelligence operators. These ranged from a special 
type of paper, useful for individual sheet destruction, 
to fittings for briefcases and notebooks, where large 
quantities of ordinary paper could be very quickly 
destroyed by either incendiary or explosive means. 
The latter had particular usefulness in the destruc- 
tion of large quantities of heavy paper, a problem 
which had always proved difficult, for paper in bulk 
is very slowly and imperfectly consumed by fire. In 
the sections below these various solutions are dis- 
cussed individually. 

20.2 DESTRUCTIBLE PAPER 1 

It was desired that a paper be developed and pro- 
duced which would be suitable for the reception of all 
types of writing on both sides. This included pencil, 
pen, and typewriter. The paper should, in addition, 
be stable to prolonged exposure to adverse conditions 
of humidity and temperature and should be very 
rapidly destroyed by mastication or by maceration in 
water. This problem was therefore not met by the 
existing Chemical Warfare Service development of a 
nitrated paper, although the latter met the above re- 
quirements except in the method of disposition. The 
nitrated paper required combustion and was, of 
course, nearly instantaneous. 

Two other papers had already been developed 
which bore on the problem. One of these utilized thin 
Japanese tissue paper called Yoshino Paper and the 
other consisted of thin sheets of cast sodium alginate. 
The first of these was unsuited because of its com- 
plete lack of wear resistance and its susceptibility to 
humidity. The latter paper was of better quality and 
was, in fact, used by British Intelligence officers. 
However, it also lacked good strength properties and, 
because of the extreme solubility of sodium alginate 


in water, was too sensitive to moisture to be satis- 
factory. The division’s contractor chose to attempt 
the coating of Yoshino Paper with a composition 
which would increase the strength and resistance to 
abrasion when dry, and yet would not prevent the 
rapid disintegration of the paper base and the coat- 
ing on maceration in water. Complete success at- 
tended this effort and a preferred coating compo- 
sition was developed as follows: 


Components 

Pounds 

Polyvinyl alcohol (RH-488) 

75 

Titanox WDL 

90 

Sorbitol lactate CRL 129 (78.5%) 

64 

Water 

300 

Alcohol (Shellacol) 

300 

Saccharin USP (insoluble) 

0.25 


Mixing of this composition in a colloid mill gave a 
mixture of the proper consistency on which the paper 
base was floated, then wiped lightly over a round 
doctpr, and carried through a low-temperature dry- 
ing oven. The procedure was practically identical 
with that used for making glue type mimeograph 
stencils. It gave a coating of 23.5 lb per ream or 
78.4 per cent on the finished paper. Exhaustive tests 
of these sheets with all types of writing under con- 
ditions of 100 F and 90 per cent relative humidity 
with and without folding and pressing indicated 
most satisfactory performance. The individual sheets 
showed no tendency to stickiness, although they be- 
came somewhat limp. Under extremely cold condi- 
tions, no loss of flexibility was observed. It was de- 
termined also that the materials employed in the 
formula were not toxic when taken by mouth or al- 
lowed to be in contact with the skin. Sheets as large 
as Sy 2 X 6 in. folded excessively into a small size 
could not be readily disposed of by chewing; however, 
smaller sheets were very quickly and easily masti- 
cated beyond the point of legibility. 2 A small pro- 
duction gave no difficulty. 

20.3 PYROFILM 3 

20.3.1 Composition and Use 

Prior to the entrance of Division 19 into this field, 
considerable work had been done by British research 
groups on the destruction of documents in despatch 
containers. For this purpose, the British had de- 
veloped a potassium nitrate quilt used in conjunction 


122 


MESSENGER POUCH DESTROYER 


123 


with a charge of thermit. Various size containers 
ranging from cigarette boxes to suitcases and cleverly 
booby trapped with elaborate switches had been de- 
vised. 4 None of them, however, performed with any 
great speed or efficiency, and an alert interceptor 
could very likely extinguish the flames before de- 
struction of the documents was complete. 

The division’s contractor developed an entirely 
new incendiary material for this purpose. This was 
dubbed Pyrofilm and was composed of equal parts, 
by weight, of nitrocellulose plastic (celluloid) and 
finely divided sodium nitrate of technical grade. It 
was demonstrated that standard size batches of this 
mixture could be mixed by ordinary machinery to 
form a block of material which, after curing and dry- 
ing, could be cut into sheets of any thickness be- 
tween 30 and 60 mil. The time required to prepare a 
250-lb block of the crude plastic was about two hours, 
and the curing time about ten days. It was suscepti- 
ble to dyeing, like similar plastics. It was remarkably 
tough and showed little alteration on exposure to 
prolonged temperature and humidity cycles. 

Investigation of mixtures employing chlorates, 
perchlorates, and dichromates indicated that none of 
them were as satisfactory as the nitrate. Some of their 
compositions burned more fiercely with more intense 
flame, but did not retain the good stability of Pyro- 
film and were harder and more dangerous to mix. It 
was found that Pyrofilm could be readily ignited by 
the flame of a match and burned steadily, though 
feebly, in the open, liberating drops of molten sodium 
nitrate. Despite its ready inflammability, it had high 
shock resistance and was not detonated by blasting 
cap or severe mechanical impact. However, in con- 
tact with any organic material such as paper, the 
liberated sodium nitrate entered into reaction with a 
very intense fire and complete destruction of the or- 
ganic material. Evidently the sodium nitrate com- 
bined with the carbon of the paper to form sodium 
carbonate and completely robbed it of its structure, 
leaving no distinguishable ash. 

20.3.2 Initiation 3 

In the devices described below, this material was 
interleaved with the papers to be destroyed and was 
provided with what amounted to an instantaneous 
incendiary Pencil (see Chapter 11). This consisted of 
a tube containing a striker loaded against a compres- 
sion spring directly above a Magnesium Matchhead. 
The striker, which was of split construction, was re- 
strained by an inserted pin. Removal of this gave 


nearly instantaneous operation of the Magnesium 
Matchhead, which immediately fired the adjacent 
sheet of Pyrofilm and initiated the device. The vari- 
ous parts of this fuze and its operation are clear from 
Figure 1. 

20.3.3 Incendiary Notebooks 6 

It was a simple matter to interleave pyrofilm 
sheets between the pages of a notebook and to 
equip that notebook with the instantaneous incen- 
diary Pencil. Two sizes of notebooks were produced; 
they are illustrated in Figure 2. 

In the assembled form the device was entirely safe, 
since the Pencil had a safety strip and required both 
a twist and a pull for operation. It was found by ex- 
periment that for complete and rapid destruction ten 
sheets of 16-lb paper should be enclosed by two 
sheets of 30-mil Pyrofilm of the same area. Since 
Pyrofilm was comparatively rigid, only a mechanical 
type of binding was practical for the notebooks, and 
the spiral type illustrated in Figure 2 was found to be 
very satisfactory. 

20.3.4 Incendiary Briefcase 

In those cases where larger quantities of loose pa- 
per required destruction, a unit package suitable for 
insertion in a briefcase was developed. This consisted 
of an accordion-type folder illustrated in Figure 3. It 
consisted of five sheets of 60-mil Pyrofilm, each sur- 
face coated with nitrocellulose by dipping in a lac- 
quer, bound together to form an expanding compart- 
mented envelope. Experience showed that such a unit 
weighing in all 2.67 lb would successfully destroy 68 
sheets of ordinary paper of typewriter size weighing 
0.61 lb. The confinement provided by the surround- 
ing briefcase was most beneficial, and the time re- 
quired for complete consumption of the contents 
was less than one minute, both in this case and in the 
case of the incendiary notebooks. Whether an alert 
interceptor could have arrested the combustion and 
recovered the papers was doubted because of the 
tendency of Pyrofilm to increase its combustion rate 
when smothered by sand or trampled on. Only the 
instant application of a large quantity of water would 
have arrested the destruction. 

20.4 MESSENGER POUCH DESTROYER 5 

Prior to the successful development of the devices 
based on Pyrofilm, a joint NDRC-CWS develop- 
ment of a messenger pouch destroyer took place. 


124 


AIDS TO INTELLIGENCE 



LOCKING STRIP 
84127 D 


BUSHING 
84127 B 


FASTENING PLATE 
84131 B 





MAGNESIUM MATCH HEAD- 
IGNITER 84132 F 



ASSEMBLY OF PLATE 
84131 B, TUBE 84131 A, 
AND BUSHI NG 84127 B, 
SOLDERED, PLATED AND 
LACQUERED. 


SAFETY PIN 
84127 C 



COMPLETE PENCIL 
B 84 I 3 3, B 84 I 3 5 . 


Figure 1 . Instantaneous incendiary Pencil. 


ERASER 
84131 F 



SECTIONAL VIEW 



EXPLOSIVE DOCUMENT CONTAINERS 


125 




Figure 2. Pyrofilm notebooks. 


This was known to OSS at the time when further 
work on the problem was requested, and it was felt 
by their officers that the Messenger Pouch Destroyer 
was too uncertain and slow in its action and too 
easily interfered with by an aggressive observer. 
Early designs of this unit were submitted by the con- 
tractor to the Chemical Warfare Service. Each of 
them was based on a celluloid case filled with an in- 
cendiary charge of two briquettes of fast-burning 
pyrotechnic (10 parts paraffin, 89 parts potassium 
perchlorate, and 1 part powdered charcoal). An ex- 
plosive element was also provided with a delay train 
built into an insulated block cut to fit one side of the 
case. 

Initiation was obtained by the use of a standard 
M-2 fuze lighter cemented to the outer side of the 
case. The unit was placed inside of the despatch 
pouch in contact with documents interleaved with 
nitrated paper and initiated by a pull on the fuze 
lighter. Following a delay of 5 sec the pyrotechnic 
burned briskly for about 45 sec and the conflagration 
of the pouch proceeded vigorously for another 2 min. 
As it began to die down, a violent explosion occurred 
scattering all traces of the charred documents. 

This device would be useful for the booby trapping 
of unaccompanied pouches, where presumably the 


element of surprise would be so great that there 
would be no time for interference with the operation 
of the Destroyer. 


20.5 EXPLOSIVE DOCUMENT 

CONTAINERS 7 8 

In the central laboratory of the division the only 
other likely method of solving the problem, namely, 
one based on explosives, was undertaken. From this 
emerged three different containers, all of them based 
on the destruction of documents by the heat and 
blast of an explosive charge. The two smaller devices 
were made from small tins and were capable of carry- 
ing two sheets and 14 sheets of folded typing paper 
respectively. 

Initiation was provided by an adaptation of the 
standard existing pull switches of either OSS or the 
Corps of Engineers. By the stab action of this switch, 
a time delay averaging 4.5 sec was ignited which in 
turn initiated the explosive charge contained in the 
bottom and top of each case. For the small case, this 
charge consisted of approximately 19 g of cast pento- 
lite; for the larger case, it consisted of 75 g of cast 
pentolite. A user would presumably carry his secret 



Figure 3. Pyrofilm envelope for brief case. 




126 


AIDS TO INTELLIGENCE 


documents in one of these small pocket-size contain- 
ers, and, when in danger of interception, would acti- 
vate the delay unit and dispose of it at once. Its sub- 
sequent explosion could be counted upon to shred 
the contents beyond legibility. 



Figure 4. Explosive briefcase destroyer. 


Neither of the smaller units was produced, since 
they were developed very late during the war; how- 


ever, there was a limited production of a larger-size 
unit suitable for insertion in a briefcase. This is illus- 
trated in Figure 4. 

This unit consisted of a sheet metal container ap- 
proximately 14 x 10x34 in. loaded with 1.85 lb of 
50/50 cyclotol (RDX-TNT), initiated by means of 
two Corps of Engineer 15-sec delay detonators which 
were ignited simultaneously by a single pull on a 
common ring. This unit had an overall weight of 
S }/2 lb and was of a size convenient for insertion in 
the center compartment of a briefcase. The docu- 
ments to be protected could be placed in the pockets 
on either side. Upon operation, it was found that 
13 ^ lb of loose paper could thus be almost instantly 
destroyed, whether the briefcase was lying on the 
ground or was suspended in air. It appeared that the 
explosive blast shredded the paper and the heat of the 
explosion consumed it, so that no fragment large 
enough to contain a printed word was ever found. 
This unit was somewhat more hazardous to the user, 
but again was provided with a time delay so that he 
might dispose of it before its action. Presumably it 
would be absolutely certain in its destruction effect, 
since the chances of an enemy being able to inter- 
fere would be very small.. 


Chapter 21 

DOG DECEPTION 


21.1 INTRODUCTION 

German Gestapo and Wehrmacht personnel em- 
ployed carefully trained dogs to hunt down and lo- 
cate suspected persons and to capture parachutists. 
The problem existed of how to thwart these dogs and 
their trainers in this pursuit, and considerable British 
work had been done along these lines prior to the 
entry of Division 19 into the problem at the request 
of OSS. Very little advance was made by the division 
over the British work, and this chapter is written 
largely to give greater publicity to the very valuable 
contributions made by our ally. 

The problem had two aspects, namely, the use of 
the proper tactics and the use of specially designed 
devices (Dog Drags) to deceive the animal. No im- 
provement was found over the British instructions in 
tactics; some improvement was found in the use of 
deceptive devices, and, if the problem were an active 
one, it was felt that a number of different chemical 
solutions could be used with advantage in the de- 
ception. 

21.2 TACTICS 2 

21.2.1 Assisting Scents 

After a dog has been given the scent of the man he 
is required to track, by smelling some article used or 
handled by the man or the room or ground where he 
has worked or slept, he begins to pick up the trail. In 
following the trail he is assisted by certain scents 
which may be listed as follows: (1) windborne scent 
traveling directly from the man to the dog, which 
may travel as much as a mile or more; (2) still air 
scent, which is left by the man in sheltered spots 
where there is little air circulation close to walls or 
under shrubs, or in similar locations; (3) track con- 
tact scent, which arises from the actual transfer of 
odor from the human skin or clothes to the ground or 
shrubs; (4) local track scent, which is caused by dis- 
turbance of the ground or crushing of the vegetation. 

Obviously the harder and cleaner and more free 
the ground is from cover, as an open paved road, the 
more feeble the contact and local and still air track 
scents ; hence, such spots or places much used by men 
or animals are unfavorable to the dog. Most favor- 
able to him are locales covered with grass, sheltered 
by hedges where the ground is soft. 


21.2.2 Preliminary Precautions 

If possible, it is advisable that the person, who may 
be tracked, is wearing clean clothing and has had a 
hot bath. Obviously this is an unlikely requirement. 
He should remember that clean rubber shoes handled 
only with clean gloves will give good protection. He 
should avoid still air scents by leaping over obstacles 
with a stout pole, riding a bicycle, or even walking on 
stilts. To avoid windward scent, he should arrange 
his starting point to be on the windward side of his 
destination or at least make a large angle with the 
direction from which the wind is blowing. 

21.2.3 Parachute Landing 

The paratrooper should dispose of his visible equip- 
ment and parachute immediately on landing and 
prior to any attempt to lay a false trail. The more 
confusion he can create doing this, by walking 
through grass and bushes, is naturally beneficial. 
Several false trails may be laid at this time. These 
trails may be quite elaborate and run to a distance of 
as much as }/% mile. Use can be made of the above 
principles laid down for different types of ground and 
places favorable for scent may be deliberately chosen. 
The sequence of trails and their relative lengths 
would vary in a given operation. 

21 . 2.1 False Trails 

The essence of a false trail is that it apparently 
continues in a direction in which the man does not 
proceed, and, in this respect, it is important to re- 
member that the dog, as well as the master, must be 
deceived. Another guiding principle is that the first 
part of the journey should not be in the direction of 
the final destination. The value of a number of false 
trails right at the start is apparent because the dog 
has little chance of selecting the proper one and valu- 
able time is lost during which all trails become fainter. 
It is desirable that false trails should cross each other 
in an acute angle and that one or more of them should 
return to the original starting point. Before getting 
off a false trail, the man should clean his shoes of any 
unusual materials contacted while on that trail. The 
time spent in laying carefully conceived false trails 
would be well repaid in the delay caused the pur- 
suers. 


127 


128 


DOG DECEPTION 


21.2.5 Clean Heel Trail 

Having reached a spot unfavorable to the dog, and 
after laying many false trails, the man should at- 
tempt a fairly long trail (400 yd) which, without de- 
ception, would be counted upon to be hard to follow 
because of the nature of the ground and the direction 
of the scent. The use of a bicycle or a clean pair of 
shoes or clothing at this point would be very bene- 
ficial. 

21.2.6 Drag Trail 

Following the clean heel trail, the man should make 
use of deceptive devices known as the Dog Drag (see 
Section 21.3). This device dragged along the ground 
behind him deposits strong chemical odors on the 
ground and presumably these would suffice to further 
confuse or irritate the dog. The use of the Drag would 
be in conjunction with a number of false trails and 
would last so long as the scent appeared strong. Pre- 
cautions in its use include assurance that none of the 
ampule contents has contaminated the person and 
that all the trail is on ground unfavorable for scent. 

Having performed the above exercises and reached 
a spot extremely unfavorable for scent, the Drag is 
slung into a tree, a pond, or a bush, and the trail is 
ended. 

21.3 DOG DRAG 

This device is illustrated in Figure 1. It consisted 
of a brass cylinder containing a glass ampule of chem- 
icals, and equipped at one end with a knurled screw 
and, at the other end, with a canvas sack. Tied to it 
was a length of rope. The brass parts of the device 
were identical with those used in the AC Delay (see 
Section 13.2). The operator was instructed to crush 
the ampule by turning the knurled screw, thus liber- 
ating the organic liquid contents into the canvas sack 
where the oily material was soaked up. In this opera- 
tion, care was exercised that the person did not be- 
come contaminated himself. The Drag was then care- 
fully placed on the ground and, by means of the rope, 
dragged behind the user until exhausted. As origi- 
nally developed, the ampule contained equal parts of 
caproic, i-valeric acids and castor oil. This solution 
was not distasteful to the dog but was an extremely 


concentrated human footy odor. The theory behind 
its use was that the dog’s nose would be so accus- 
tomed to this very powerful odor that when the Drag 
trail ended he would be incapable of picking up the 
very faint footy odor of the final clean heel trail. If all 
the precautions given in Section 21.2 were followed, 
this was likely to be the case, but in numerous field 
trials 3> 4 success was variable, depending upon the 
dog and the skill of the Drag user. 



Figure 1 . Dog Drag with ampule removed. 


Attempts were made to improve the Drag by the 
substitution of other chemicals in the ampule solu- 
tion. Among these were examples of chemicals calcu- 
lated to paralyze the dog’s sense of smell, to cause 
pain, to tire the dog, to arouse emotions, to distract 
the dog, and to repel him. None of the chemicals cal- 
culated to produce these effects turned out well. Of 
them all, only four would seem to warrant further 
consideration by future users. These were a-ionone, 
fresh grass juice, nicotine sulfate, and thioglycollic 
acid. 1 It was not demonstrated that any of these 
chemicals were superior to the original British com- 
position and, in fact, the conclusion of the work was 
that the chemicals were secondary in their impor- 
tance to the tactics. It was concluded also that, with 
the proper tactics and with or without the slight 
assistance of Dog Drag, a skillful man could elude the 
best trained dogs if his trail were more than Yi to 
1 hour old before the hunt began. 

Only one significant improvement was made in the 
British procedure. This was in the recommendation 
that clean paper bags 5 should be tied over the feet 
when a clean heel trail was begun. Thereby, of course, 
the contact odor was nearly eliminated. 


Chapter 22 

WATER PURIFIER 


22.1 INTRODUCTION 

Although a great deal of work on the problem of 
supplying the individual soldier in the field with ster- 
ile, attractive water had been done by such compe- 
tent groups as the Surgeon General’s Office, the Quar- 
termaster, the Bureau of Medicine, and the Com- 
mittee on Medical Research, Division 19 at the re- 
quest of OSS made a survey of existing methods from 
the point of view of that group’s requirements and 
did a certain amount of original work, which is the 
subject of this chapter. 

The operational requirement stated to the division 
at first was later modified in the light of attainable 
performance. It was hoped, however, that a man on 
his own in the jungle country of Southeast Asia could 
supply himself for a period of one month with taste- 
less, sterile, colorless, odorless water, from the very 
unattractive streams of that region, and with the 
minimum quantity of accessory equipment. At the 
start, it was desired that this be accomplished with- 
out the use of chemicals such as the standard Hala- 
zone tablets issued in the Army (chloramine-T) or 
more modern substitutes such as C-DC (chlor-dechlor 
tablets, a product of the Wallace and Tiernan Com- 
pany) or Bursoline (triglycine hydrotriiodide, a de- 
velopment of the Committee on Medical Research). 
This hope was abandoned in view of inability to in- 
sure sterility by filtration alone without chemical 
treatment. 

A survey of existing portable mechanical filters dis- 
closed three of promise which had been extensively 
tested by the services. 2 These were known as the 
Quinn Microfilter, the Wallace and Tiernan Portable 
Filtering Device, and the Bowser Piston Pump. The 
first and last of these depended upon ceramic materi- 
als for the main filtration and chlorination with Hala- 
zone for final sterilization. The Wallace and Tiernan 
unit was based on a renewable asbestos filter pad 
containing activated charcoal. It also depended on 
chlorination by the use of C-DC tablets which gave 
super-chlorination followed by chemical removal of 
the excess chlorine to give a potable solution. Using 
this device as a basis, the division’s central labora- 
tory investigated the use of a number of types of 
filter materials including ceramic plugs, porous silver 
metal disks, and beds of activated charcoal. 

From Section 22.2 it will be seen that no basic im- 


provement on the Wallace and Tiernan model was 
forthcoming, and this appeared to be the best of the 
three available designs. However, a redesign of the 
Wallace and Tiernan unit was made to produce a 
smaller, lighter device of more capacity, better suited 
for the use of an individual (Section 22.3). 

The remaining work of the division was concerned 
with attempts to generate by means suitable for field 
use sufficient ozone to produce sterile, colorless, and 
odorless water directly. It was realized that the ef- 
fectiveness of ozone for this work might be open to 
question. From purely chemical grounds, however, it 
appeared after investigation to be an unlikely method 
in any case. The results of that work are given in 
Section 22.4. 

22.2 FILTRATION STUDIES 

22.2.1 Ceramic Plugs 3 

Using suspensions of mud and Aquadag (colloidal 
carbon) in water, a great number of ceramic and 
porcelain filters were tested for rate of flow and ef- 
fectiveness of filtration. Extremely variable results 
were obtained, even between examples of the same 
ceramic material. This indicated an uncontrollable 
variation in porosity and the danger of the develop- 
ment of minute cracks which were not easily located, 
but were easily formed because of the fragility of the 
materials. 

It was found that the effectiveness of such plugs 
decreased very markedly with continued use, so that 
the rate of flow which, at the start, might be a reason- 
able figure under an attainable pressure of about 
50 psi would drop in the course of a few minutes to a 
value of as little as ooo the original rate. Regenera- 
tion or cleaning of such filters was moreover very diffi- 
cult, for backwashing under pressure did not usually 
fully restore the ceramic. Furthermore, if such plugs 
were allowed to dry with the adhering coat of mud, 
it became even more difficult to regenerate them. 

It was thought that perhaps improved perform- 
ance could be obtained by a pre-filter which would 
effectively remove the bulk of the insoluble suspen- 
sions. In this way, the ceramic filter would be saved 
for the removal of the last traces of very fine ma- 
terial. Pre-filters such as the Millbank Bag 4 were 


129 


130 


WATER PURIFIER 


somewhat effective but were felt to be too slow in 
their operation. More success was had with pre- 
filters consisting of beds of powdered metal and of 
charcoal. Grade B aluminum grain appeared to be 
the best of these materials, although it was difficult 
to make exact conclusions, since performance de- 
pended so largely on the turbidity of the water. It 
seemed possible that 40 qt of water containing 50 
parts per million of fine mud could be clarified with a 
filter of this type having an area of 58 sq in. without 
backwashing, but merely by scrubbing the surface of 
the porous disks holding the aluminum powder. Gyp- 
sum, precipitated barium carbonate, and barium sul- 
fate did not appear promising, although their trial 
was suggested by the thought that negatively charged 
viruses would be precipitated by positively charged 
adsorbents. It was expected that activated carbon 
would be used in any case to remove poisons, odors, 
and colors from the water by adsorption, but experi- 
ments with a variety of carbon preparations made it 
appear very doubtful that carbon would be any more 
effective in this regard than as a pre-filter of large 
particles. Pre-filters made of glass cloth, Nylon, and 
linen were all open to objections raised against the 
Millbank Bag and trials showed considerable tend- 
ency to clogging and very inefficient performance. 

It was decided that ceramic plugs, with or without 
pre-filters, held no promise for the construction of 
rugged portable units of reasonably long life. 

22.2.2 Metal Plugs 3 5 

It was proposed to circumvent some of the difficul- 
ties encountered with ceramic plugs by the use of 
metal plugs formed by powdered metallurgy. It 
seemed possible that the porosity could be better con- 
trolled and, very likely, that these plugs would be 
completely resistant to breakage. Moreover, it was 
hoped that, if they were made of metals such as silver, 
a certain bactericidal action due to the metal surface 
would perhaps give sterile water by filtration alone. 

Using a series of silver disks of known porosity, 
studies were made with clay suspensions. It was 
found that resistance offered by the accumulating 
filter cake of deposited clay was practically the same 
for all disks regardless of pore size. This led to the 
assumption that finely porous metal disks behaved in 
the optimum manner; that is, they were fine enough 
to hold the clay particles and were uniformly porous 
enough to spread the resulting filter cake evenly on 
the surface, giving the minimum thinness and maxi- 
mum rate of flow. Tests with regenerating such filters 


by back pressure and scrubbing under running water 
showed that the disks could be restored to about 34 
their original efficiency without trouble. However, 
when organic material was added to the suspension 
of clay, the flow rate could not be maintained by this 
means and it required heating of the disk nearly to 
red heat to restore the disk to its original usefulness. 
Silver disks used in conjunction with pre-filters gave 
somewhat better performance. 

At this stage attention was paid to the sterility of 
the water passing through such disks to determine 
whether the disks were bactericidal. The results were 
variable and not related to pore size. Some disks pro- 
vided sterility in some trials and not in others, and 
the only effectiveness of the silver appeared to be in 
preventing growth of bacteria through the filter, 
which was an additional handicap of the ceramic 
type. 

It was concluded that porous silver filters, while 
seeming to have points superior to ceramic materials, 
were not satisfactory because of the tendency to clog, 
with or without pre-filters, because of the variable 
performance against organisms, because of the prob- 
able excessive weight of the powerful pump required 
for an effective unit, and because of the mechanical 
complexity of designing an individual light, portable 
filter based on them. 

22.2.3 Filter Pads 5 

Among the pre-filters tried, had been the type used 
by the Wallace and Tiernan Company for their port- 
able unit and known as Seitz K5 Pad. Further trials 
of this showed that it had high retentiveness and good 
resistance to clogging, while retaining a rapid flow 
rate. Interestingly enough, it also showed fair ability 
to give sterile filtrates, although it was not entirely 
reliable. It appeared that this would be the best filter 
on which to base a portable unit, provided a redesign 
of the pump could be made in the interest of lower 
weight and lower unit output. 

22.3 MECHANICAL DESIGN 2 

Using the general features of the Wallace and Tier- 
nan device and depending upon the Seitz K5 Pad for 
filtration, a small pump and filter unit was con- 
structed as shown in Figure 1. The device consisted 
of a diaphragm, pump, and a filtrate collector and a 
filter supporting vessel, which were drawn tightly 
together by a ring clamp screw to confine the filter 
disk on a perforated metal disk. A number of the 


OZONE STUDIES 


131 


parts were the same as those used in the Wallace and 
Tiernan Device. 

The intake and exhaust valves were both located 
in the main pump body. The intake valve assembly 
was made of Monel metal, and the valve was fastened 
with a rubber washer cemented to the metal and held 
by a screw. The exhaust valve led through the middle 
of the pump body and into the filter chamber. The 
main pump body, the diaphragm plates, the clamp 
ring, the filtrate receiving vessel, and the perforated 
plate were all of aluminum. The device weighed 13 oz, 
had a maximum diameter of 3.84 in. and a height of 
2.19 in., a size convenient for pocket carrying. The 
intake tube was 5 ft of %6~in. rubber tubing, the two 
ends of which were attached to the tubulature of the 
pump and to an intake strainer and float, which 
served to remove gross contamination and to protect 
the valve and pad by pre-filtration. This strainer con- 
sisted of a sock of olive drab Nylon cloth on a spring 
frame. It floated about 1 to 6 in. below the surface by 
attachment to a cylindrical cork float. The water 
drawn by the pump therefore came from close to the 
surface, where it was relatively free of suspended 
matter. 



Figure 1. Small filter-type water purifier. 


The pump had a capacity of 2 cu in. per stroke and 
required 30 strokes per qt of water. It was self-prim- 
ing and foot-operated. The pressure developed de- 
pended upon the operator’s weight and in lb per sq in. 
was roughly 34 his weight in lb. Using a clean filter 
pad with clear water, the optimum pumping rate was 
1 qt per min. The effort required was not tiring. The 
filter pads were circular, 3^4 in. in diameter. Its per- 


formance on moderately turbid semi-stagnant pond 
water is given below. 


Table 1. Time required for delivery. 


Quantity 

Time 

First quart 

1.08 min 

Second quart 

1.5 min 

Third quart 

2.08 min 

Fourth quart 

3.5 min 

Fifth quart 

5.1 min 


Seventy-two pads weighed 1 lb, and, while the raw 
water to be filtered and daily requirements would 
vary considerably, one pad per day was estimated to 
be sufficient for use, hence, one of these pumps with 
1 lb of pads and the necessary chemicals for water 
sterilization would provide filtered water for at least 
60 days at a total weight of not over 2 lb. The chem- 
icals recommended could be any of those ordinarily 
used. It seemed to the workers in the division that if 
Bursoline were standardized by the Surgeon Gener- 
al’s Office this would be the best choice. Failing that, 
the C-DC tablets of the Wallace and Tiernan Com- 
pany appeared most suitable for quick sterilization. 

22.4 OZONE STUDIES 6 

22.4.1 Evaluation of Ozone 

Previous work 1 indicated that ozone might have 
value as a chemical capable of producing sterile 
water in very brief periods of time and in very small 
amounts (10 mg in 1 liter of water). It was hoped that 
a simple way of generating ozone in the field could be 
discovered for the individual soldier’s canteen use. 
This treatment would presumably, not only yield 
sterile water, but would remove the color and odor 
associated with river water. Excess ozone would not 
be harmful to the individual in contrast to chlorine. 
It was realized that the true effectiveness of ozone 
against all types of organisms and viruses was not 
known. Fortunately, or unfortunately, the necessity 
of investigating this point never arose, since no prac- 
tical method of generating ozone in the field by port- 
able equipment could be found. 

22.4.2 Preparation by Oxidation of 

Phosphorus 

A survey of the chemical literature indicated that 
a good yield of ozone might be obtained by the oxida- 
tion of white phosphorus in a rapid stream of moist 
air in the dark. With the rate of flow varying from a 
few milliliters to several liters per minute, the amount 


132 


WATER PURIFIER 


of ozone obtained was found by test to be about 1 mg 
per hr. This rate of production was obviously too low 
to make the method practical. 

22.4.3 Electric Discharge 

The chief industrial source of ozone for water 
sterilization is silent electric charge. Voluminous lit- 
erature on the subject exists. Conceivably a small 
hand-operated electro-mechanical device could be 
designed which might produce ozone directly from 
the air by means of this principle. The possibility was 
not investigated. 

22.4.4 Preparation of Persulfates 

The persulfates as a class in acid solutions liberate 
ozone. It was hoped to find the optimum conditions 
for this reaction and perhaps to prepare tablets which 
would spontaneously react to give a quantity of 
ozone sufficient to sterilize a single canteen. Tests 
definitely confirmed the generation of ozone by this 
chemical reaction, at temperatures, however, which 
were not attainable conveniently in the field (70 C). 
It was felt that the mechanical difficulties of devising 


an apparatus suitable for use with the reaction were 
insurmountable. Unfortunately, the yield of ozone 
was 5 per cent, the yield of oxygen 95 per cent, from 
the reaction. If a catalyst could have been found 
which would have reversed these figures, the chemical 
method would have been a possibility. 

22.4.5 Preparation by Electrolysis 

It was found that a portable generator operated by 
hand, motor, or storage battery could provide suffi- 
cient ozone to be useful. However, this meant con- 
siderable equipment, with increase in weight and loss 
of smallness and compactness; hence, although ex- 
perimentally feasible, the method was not felt to lend 
itself well to actual field use. It was calculated that a 
6-v storage battery by electrolysis of a 1.2 specific 
gravity sulfuric acid solution using a lead jar for the 
cathode and a 1-centimeter lead disk for the anode 
and having a total volume of 1 liter would provide 
1 liter of sterile water every 5 min. The device would 
be susceptible to traces of impurities and would obvi- 
ously not answer the original field requirement. It 
might warrant further study for use at a fixed camp, 
but only if ozone were to be evaluated as a sterilizing 
agent. 


Chapter 23 

QUIETING OF OUTBOARD MOTORS 

23.1 INTRODUCTION cured by methods usable in the field. Both of these 


A desire was expressed to Division 19 by OSS and 
British liaison officers 3 assigned to it for development 
work on the silencing of outboard motors which were 
already in use in the field for reconnaissance work. 
These motors were employed with small craft, for the 
purpose of effecting landings on enemy-held coasts by 
men assigned to gather information and later were 
required for their escape. It was important that the 
coast be approached with a minimum of noise and 
that the escape attract no attention. 

The motors already used were four in number: the 
Johnson POLR 22 hp, the Johnson K 9.8 hp, the 
Evinrude Lightfour 9.7 hp, and the Keikhaefer Mer- 
cury Rocket 6 hp. The problem was essentially the 
development of silencing kits which could be shipped 
to the field and installed on motors already issued. 
It was not the problem of devising a silent outboard 
motor. The work resulted in considerable improve- 
ment in the performance of all the above with the 
exception of the Johnson K. 

Much later in the program, Navy groups in Cali- 
fornia at the San Diego Navy Yards asked for and 
received support in the silencing of 50-hp Evinrude 
motors used by the Navy with 32-ft Chemold Plastic 
surf boats. The principles discovered in the original 
work were successfully applied in this new problem. 

The program was handled for Division 19 by the 
Engineering and Transition Office of OSRD, and, 
through that office, the support of Section 17.3 and 
the Electro-Acoustic Laboratory at Harvard Uni- 
versity, as well as a group at the University of Cali- 
fornia at Los Angeles, were secured. Without the 
active cooperation of the Engineering and Transition 
Office and these assisting laboratories, the program 
could not have been successful. 

23.2 METHODS OF APPROACH 

Two entirely different methods of solving the prob- 
lem presented themselves and were used by the dif- 
ferent groups. The contractors in the east preferred 
to analyze the sources of sound and to silence them 
individually. 1 - 2 The contractor in the west preferred 
to silence the motor by any conceivable means 4 - 6 
and then to back off from the ultimate obtainable 
performance to the performance which could be se- 


me thods eventually came to the same conclusion. 

An arbitrary decision was made to eliminate from 
consideration noise caused by the boat. This included 
the boat’s acting as a sounding board for transmitting 
the motor vibrations to the atmosphere and also the 
considerable noise due to the passage of the boat 
through water and against waves. No attempts were 
made to develop a boat of the best design for silence. 

The early tests were conducted in a Jury Rig and 
sound measurements were taken in a number of dif- 
ferent positions by an ERPI Sound Frequency Ana- 
lyzer. Analysis of the noise spectrum was made from 
10 to 10,000 cycles. Absolute noise levels were de- 
termined. The unsilenced engines were thus found to 
behave as shown in Figure 1. 

Tests were also made in which the various motors 
on actual boats, when going directly away from a 
beach, were evaluated by a listening jury. Table 1 
gives the performance of the unsilenced motors under 
these conditions and the peak engine rotation fre- 
quencies. All these distances were measured at full 


Table 1 . Performance of unsilenced motors traveling 
from beach. 


Motor 

High peaks 

Maximum 
distance heard 

POLR 

86 (333 cps) 

2,930 ft 

Mercury 

79 (267, 533, 667 cps) 

2,400 ft 

K 

73 (400 cps) 

1,800 ft 

Lightfour 

74 (400 cps) 

1,300 ft 


throttle. The serious need for sound reduction is very 
apparent from this table. 

23.3 NOISE SOURCES 1 2 


23.3.1 Exhaust 

This was the most obvious source of noise. In most 
of the motors, it was taken care of by underwater ex- 
haust. In the 22-hp Johnson POLR, this was the case 
and the demonstrable reduction in noise level at all 
harmonics averaged roughly 10 db. Comparable re- 
sults were not obtained with the Johnson K. In this 
case the underwater exhaust created a burble which 
appeared to be due to the breaking of the exhaust 
bubbles against the water surface. Attempts to alter 
their size and distribution by insertion of various 


133 


134 


QUIETING OF OUTBOARD MOTORS 



FREQUENCY OCTAVES IN CPS 

Figure 1 . Comparison of sound levels of standard 
engines. 

plates and auxiliary expanding chambers were quite 
unsuccessful. The dragging of a blanket on the sur- 
face of the water also was without effect. Even a 
muffler five times the normal volume produced only 
minor improvements in this characteristic burble. 
The source of this difficulty was never accurately 


placed, in spite of underwater sound measurements, 
and the motor was finally abandoned as incapable of 
being silenced because of this peculiarity. It was the 
only failure among the motors. 

In the Evinrude Lightfour, a high percentage of 
noise was lost in the underwater exhaust in and above 
the slip stream of the propeller. Slight additions to 
the standard motor consisted of mufflers based on 
either a tube connecting annular chambers between 
washers equally spaced or a similar tube containing 
rolls of copper screening to provide quick cooling of 
the exhaust cases. The Evinrude exhaust system 
made use of a relief, which passed a small percentage 
of exhaust during starting and idling. At full speeds 
this passage was flooded with water and the exhaust 
was entirely underwater. In the Mercury, this escape 
feature provided so much relief that the underwater 
feature was entirely ineffective, and it was necessary 
to design a new exhaust manifold incorporating the 
Evinrude exhaust relief. The results were gratifying. 

23.3.2 Intake 

The second largest source of noise came from the 
carburetor intake. This was effectively silenced, in 
the case of all motors, by the use of a single-chamber 
resonant type silencer, which was attached to the in- 



Figure 2. Noise level in 5-cycle band in decibels at 46 feet. 


RESULTS 


135 


take manifold. Figure 2 shows the performance on 
the Evinrude Lightfour of two different models of 
intake silencers. A considerable reduction at all har- 
monic frequencies is apparent. 

23.3.3 Mechanical 

It seemed obvious that one would attempt the 
silencing of an outboard motor by enclosing the body 
as completely as possible in a housing. Several at- 
tempts were made, including wooden and plastic 
housings filled with insulating materials such as glass 
wool, felt, and special acoustic fillings. At the same 
time, less cumbersome tailor-made jackets called 
Barneys were tried which were intended to accom- 
plish the same purpose but which were not so bulky. 
It was found that the more elaborate housings were 
somewhat superior in noise reduction, but not suffi- 
ciently so to warrant their use in preference to the 
Barneys, which were included in the kits sent to the 
field. A typical Barney is illustrated in Figure 3. 



Figure 3. Barney. 


The Barneys were tailored to fit the individual 
power heads and were supported over hot spots of 
the motor by a shroud of perforated sheet aluminum. 
Coverage was made as complete as possible by lacing, 
and sound absorption was accomplished by lining 
with glass wool or acoustic felt; the outer material 
was glass cloth. The effectiveness of a typical Barney 
can be seen from Figure 4. 

23.4 RESULTS 

The microphone tests showed that there was a di- 
rectional pattern of motor noise and that noise levels 
would be somewhat higher in positions directly on 
either side of the boat with the least noise reaching an 


observer directly in front of the approaching boat. 
These differences, however, were too small to be sig- 
nificant. When all three of the methods of quieting 
were applied to all motors, the following maximum 
noise reduction was obtained: 


Table 2. Maximum noise reduction on quieting of 
outboard motors. 


Motor 

Noise level at 25 ft 
Unsilenced Silenced 

Noise 

reduction 

Johnson POLR 22 hp 

95 db 

69 db 

26 db 

Johnson K 9.8 hp 
Evinrude Lightfour 

79 db 

74 db 

5 db 

9.7 hp 

76 db 

63 db 

13 db 

Mercury 6 hp 

80 db 

59 db 

26 db 


This clearly shows the success which attended all 
the silencing work with the exception of the John- 
son K motor, which was abandoned. The figures were 
obtained using a 40-db weighting net. 


o u 



FREQUENCY OCTAVES IN CPS 

Figure 4. Comparison between sound level of a stand- 
ard engine with and without Barney. 

The difference in sound detection with different 
engine speeds was remarkable. Thus, in the presence 
of surf noise, quieted engines were undetected by 
listeners at 100 yd, when proceeding at a slow speed, 
but were detected at 300 yd at full speed. It was not 
clear whether the noise detection was caused by the 
motor or by the considerable noise created by the 
boat in the waves. Listening conditions such as wind 
direction, air temperature, and ambient noise level 
would, of course, vary with resultant variance in per- 
formance. It was felt, however, that the POLR, for 


136 


QUIETING OF OUTBOARD MOTORS 


example, could approach, without being heard, to 
approximately 1,400 ft at full throttle and 280 ft at 
dead slow speed. 

The performance obtained with the 50-hp Evin- 
rude and 32-ft surf-landing boats using an improved 
Barney, an improved intake silencer, underwater ex- 
haust, and some attempted isolation of the motor 
from the stern of the boat gave comparable results. 
A maximum reduction in noise of 54 db was obtained, 
and it was calculated that with a background noise of 


64 db such a boat could approach to a distance of 
150 yd before being detected above the ambient 
noise conditions. 7 

Sample kits suitable for the silencing of the three 
successful motors originally proposed for study were 
dispatched to the field, and a small production under- 
taken by OSS. Information was also supplied on easy 
starting of outboard motors, 5 since this too was a 
problem with the users of the motors on reconnais- 
sance missions. 


GLOSSARY 


AC Delay. Acetone Celluloid time delay. 

Adhesive. Material used for the attachment of explosive 
charges. 

Alcoa. Aluminum Company of America. 

ARB. Army Rescue Boat. 

Barney. A glass-cloth padded jacket for covering outboard 
motors. 

Beano. A baseball hand grenade filled either with high ex- 
plosive or white phosphorus. 

Bursoline. Triglycine hydrotiiodide, a compound for water 
purification. 

C-DC. Chlor-dechlor tablets for water purification. 

City Slicker. An oil slick igniter. 

Clockwork. Precise waterproof time delays. 

Cordura. A regenerated cellulose fiber. 

CSR. City Slicker, rectangular. 

CST. City Slicker, triangular. 

Dog Drag. A device for throwing bloodhounds off the trail of 
an agent. 

FBI. Fast Burning Incendiary. 

IFL. Induction Field Locator, an electromagnetic device on 
which men equipped with IFT could home. 

IFT. Induction Field Transceiver, an electromagnetic device 
for short range secret communication. 

ISRB. Inter-Services Research Bureau, British counterpart to 
the Office of Strategic Services. 

KOFQR. Cough Mixture, an alloy of sodium and potassium 
suspended in benzene in a frangible glass container. 

Lulu. A disperser-igniter for inflammable dusts. 

Matchhead. A waterproof attachment for the Pencil time 
delay giving silent ignition of incendiary devices. 


MRL. Maryland Research Laboratories, the central labora- 
tory of Division 19. 

MWT. Microwave transmitter, a device for secure communi- 
cations over short distances. 

OSS. The Office of Stragetic Services. 

Paul Revere. An incendiary functioning either on land or on 
water and capable of igniting crude oil as well as more 
combustible materials. 

Pencil. A chemical time delay for activation of explosive or 
incendiary devices or charges. 

Permanente Mix. Incendiary filling of the City Slicker and 
Paul Revere. 

PR. Paul Revere, a form of the City Slicker. 

PVC. Polyvinyl chloride; tubes in which Pencils were pack- 
aged. 

RD-44-41 and RD-43-141. Compositions of adhesives. 

Salex. A Slow Burning Explosive composed of sulfur, alumi- 
num, and TNT. 

SBX. Slow Burning Explosives. 

Sleeping Beauty. A one-man underwater craft developed by 
ISRB. 

Spigot Mortar. A silent flashless weapon developed by ISRB. 

SR. Signal Relay (Time Pencil). 

SR A. Signal Relay American. 

SRI. Signal relay incendiary. 

SSR. Spin stabilized rocket. 

Sympathetic Fuze. A device for activating one explosive 
charge by the firing of another. 

UWT. Telegraph and telephone devices for communicating 
under water. 

WP Beano. Beano filled with white phosphorus. 


137 
















































































































































































*• 
































































































BIBLIOGRAPHY 


Division 19 reports have not been microfilmed. For access to the microfilm of other divisions and to the STR index 
volume, consult the Army or Navy agency listed on the reverse of the half-title page. 

PART I 

Chapter 1 


1. Launching M6A3 Rockets from Their Tubular Cardboard 
Containers , K. S. Pitzer and R. E. Wood, Maryland Re- 
search Laboratory, Report 100, June 30, 1944. 

2. Report of Functional and Acceptance Trials of Sight , Re- 
flecting, 2.36 " Rocket, R. H. Forbes, Research and De- 
velopment Branch, OSS, May 9, 1945. 

3. Rocket Launcher, R. E. Wood, MRL Report 239, Aug. 25, 
1945. 

4. Adaptation of the 3.5 " Rocket Launcher to Use with 2.36" 
{Bazooka) Rockets (Memorandum), R. E. Wood, Apr. 13, 
1945. 


5. Rocket Fundamentals , Div. 3 Report ABL-SR4, OSRD 
3993, 1944. 

6. The 3.5"-Spin Stabilized Rocket, CIT Report OBC 
41.1, Oct. 25, 1944, and CIT Report JBC-31, Mar. 15, 
1945. 

7. Report on 2.36 " Rocket, Ordnance Research Center, Aber- 
deen, Md., Feb. 8, 1944. 

8. Manufacturing Specifications, prepared by the Re- 
search and Development Branch of OSS, will be found 
in the files of the Strategic Services Unit of the War 
Department. 


Chapter 2 


1. The City Slicker and Paul Revere , L. F. Fieser, Final Re- 
port, OEMsr-1214, Division 19, Serial No. 30, Part II, 
May 28, 1945. 

2. Reports of the Petroleum Warfare Department, London. 

3. Anti-Flame Barrage Trials, British Report D.M.W.D. 
34/6, 1942. 

4. Trial PR Production (Memorandum), L. F. Fieser, Nov. 
6, 1944. 

5. Comments on Possibilities of Starting and Feeding Fires of 
Petroleum Film on Harbor Waters, M. P. O’Brien, College 
of Engineering, University of California, Feb. 1, 1943. 


6. Experiment of the City Slicker at Little Beach Cove, N. J. 
(Memorandum), F. R. Frazee, OSS, June 12, 1944. 

7. Fieser Oil Slick Igniters, R. E. Wood, MRL Report 83, 
May 10, 1944. 

8. Eglin Field Tests of the Permanente Igniters (Memo- 
randum), L. F. Fieser, Harvard University, May 24, 
1944. 

9. Complete manufacturing specifications as well as a mo- 
tion picture with sound track will be found in the files 
of the Research and Development Division of OSS, now 
in the Strategic Services Unit of the War Department. 


Chapter 3 


1. Beano — An Impact Type Hand Grenade , Joseph L. Boon, 
Final Report, OEMsr-1254 with Eastman Kodak Co., 
Div. 19, Serial No. 32, July 21, 1945. 

2. Memorandum on Modification of British Army Fuze 247, 
H. H. King, August 1943. 

3a. Beano, K. S. Pitzer, Memorandum from Maryland Re- 
search Laboratories to H. M. Chadwell, Sept. 28, 1943; 
Beano Throwability of Cylinders Compared to Spheres, 
R. E. Wood, D. E. Severson, MRL Report 47, Feb. 16, 
1944; Final Report on Throwing Tests Conducted in Con- 
nection with the Development of the Beano, R. E. Wood, 
MRL Report 129, Aug. 31, 1944. 

3b. Throwing Tests on Inert Beano Loaded to 12, 14, 16 and 
18 Ounces, R. S. Livingston, MRL Report 225, July 12, 
1945. 

4. Memorandum on the ISRB Allways Fuze, Drawings and 
Specifications, H. H. King, HHK/261, 264, 267, 290, 291, 
Oct. 13, 1943; Comments on the American Allways Fuze 
T-5, H. H. King, Apr. 25, 1944. 


5. Memorandum on Preliminary Studies of Fragmentation of 
Spherical Grenade Cases of Steel and Aluminum, E. H. 
Eyster, Oct. 19, 1943. 

6. Influence of Needle Point Contour on the Initiation 
of Detonators, C. Dodd, British Report 287/PR/93 
(S.R.l). 

7. Beano, Summary of Experiments and Tests Carried Out on 
Handmade Models, L. H. Farinholt, Explosives Research 
Laboratory, Jan. 25, 1944. 

8. Memorandum on Existing Grenade Comparison, R. T. 
Ellington, Div. 19, NDRC, Mar. 9, 1944. 

9. Test of Grenade, Hand, T-13 {Beano), Aberdeen Proving 
Ground Report 471.61/390(c), Mar. 27, 1944; Appendices, 
May 2, 1944. 

10. Picatinny Arsenal Memorandum 00 471.61 398(c), Apr. 
20, 1944. 

11. Memorandum on Fragmentation of Complete Beano Gre- 
nade, A. A. Layton, Explosives Research Laboratory, 
Bruceton, Pa., May 3, 5, 1944. 



139 


140 


BIBLIOGRAPHY 


12. Fragmentation Pattern of T-13 Hand Grenade Detonated on 
Firm Sand , Gustaf Hammar, MRL Memorandum, May 
6, 1944. 

13. Fragment Penetration of Clothing , Gustaf Hammar, MRL 
Memorandum, May 13, 1944. 

14. Fragmentation Test , Grenade, Hand , Fragmentation, T-13, 
Picatinny Arsenal Technical Group, Record 201, June 6, 
1944. 

15a. Development of Initiator for Beano, G. Hammar, MRL 
Report 99, July 5, 1944. 

15b. Development of Fuse for Beano, G. Hammar, MRL Re- 
port 106, July 8, 1944. 

16. Letter, W. G. Hutchinson, University of Pennsylvania 
School of Medicine, to Joseph L. Boon, Eastman Kodak 
Co., July 12, 1944. 

17. Packing for Grenade, Hand, T-13, Aberdeen Proving 
Ground Report 471.61 /497(c), July 10, 1944. 

18. Fragment Damage from Typical Shells and Bombs, M. 
Morse and W. R. Transue, TDRS 28, May 27, 1944, and 
TDRS 62, May 3, 1945. 

19. Beano Delay Fuze, Gustaf Hammar, MRL Report 140, 
Sept. 20, 1944; A Time Fuze for the Beano Grenade, 
G. Hammar, MRL Report 224, July 12, 1945. 


20. Tentative Acceptance Requirements, T-5 Fuze for T-13 
Grenade, Ordnance Department, Oct. 3, 1944. 

21. Grenade, Hand, T-13, Infantry Board Reports 1621-A 
and 1621-B, Fort Benning, Ga., May 26, 1944, and Nov. 
3, 1944. 

22. Memorandum by Subcommittee on Ammunition to 
Ordnance Technical Committee, Dec. 9, 1944. 

23. Re-inspected Fuze, Hand Grenade T-5 (Memoran- 
dum), Aberdeen Proving Ground, 471.82/43049, Jan. 4, 
1945. 

24. Memorandum by Subcommittee on Ammunition to 
Ordnance Technical Committee, June 15, 1945. 

25. Report of Mountain and Winter Warfare Board Test 57, 
Apr. 22, 1944. 

26. Fuze, Hand Grenade T5E2 for Grenade, Fragmentation 
T-13, Aberdeen Proving Ground Memorandum Report. 

27. Flash Powder Beano, D. C. Rosen, MRL Report 217, 
June 21, 1945. 

28. Preliminary Instructions for Fragmentation Hand Grenade 
T-13 with Hand Grenade Fuze T-5 or T5E1, War 
Department Technical Bulletin TB 9X-95, Feb. 5, 
1945. 


Chapter 4 


1. Final Report on WP Beano, H. J. Billings and B. B. 
Fogler, Jr., Div. 19, Serial No. 22, Part VIII, Sept. 5, 
1945. 

2. Progress Report to March 15, 1944, Arthur D. Little, Inc. 

3. Progress Report March 15 to April 15, 1944 , Arthur D. 
Little, Inc. 

4. Progress Report April 15 to May 15, 1944, Arthur D. 
Little, Inc. 

5. Acceptance Tests Applied to W. P. Beanos, R. S. Living- 
ston, MRL Report 78, May 2, 1944. 

6. T entative Requirements for WP Grenades of the Beano Type, 
Grenade Section, Ammunition Division, Army Ordnance 
Department, May 25, 1944. 

7. Division 10 Summary Report, II, p. 26, June 14, 1944. 


8. Letter, W. C. Kabrich, Office of Chief, CWS, to W. C. 
Lothrop, Technical Aide, Div. 19, Aug. 4, 1944. 

9. Note to WP Beano File, Conference in Boston, Mass., 
W. C. Lothrop, Aug. 24, 1944. 

10. The Burning Properties and Anti-Personnel Effects of 
PWP, D. G. Edwards and others, Div. 10-165, Sept. 15, 
1944. 

11. Notes on WP Beano Conference in Boston, Massachusetts, 
W. C. Lothrop, Jan. 5, 1945. 

12. Metallurgical Report, E. Kerschen, Bohn Aluminum and 
Brass Co., Feb. 1, 1945. 

13. Metallurgical Laboratory Report NN-1, G. C. Eldridge, 
Aluminum Company of America, Feb. 16, 1945. 

14. CWS Report, Edgewood Arsenal Technical Report 28. 


Chapter 5 


1. The Development of a Tree and Plate Mounted Spigot 
Mortar, H. M. Jacklin and E. J. Breech, Final Report, 
OEMsr-1279, Div. 19, Serial No. 26, Feb. 13, 1945. 

2. Reports on American Production, Major Ramsey Green, 
R. E., May 4, 1944 and May 21, 1944. 

3. Spigot Gun Fuze, British Report QX-293, June 9, 1944. 

4. Report on User Trial of the Tree Spigot Gun, held between 
January and April 1944, British Report R-2309. 

5. Acceptance Trial Tests of Spigot Mortar on Locomotives, 
F. H. MacKenzie, Oct. 19, 1944. 

6. Memorandum on Tree Spigot, L. B. Ewen, Oct. 28, 1944. 

7. Memorandums on Tree Spigot Mortar, L. B. Ewen, Oct. 
2, 1944 and Nov. 16, 1944. 


8. Mortar, Spigot — % Inch, Visit to Fort Benning, Georgia, 
L. B. Ewen, Feb. 10, 1945. 

9. Tree Spigot Bombs — Notes on Performance, JLB/EXQ/- 
9008, Feb. 12, 1945. 

10. Loading of Spigot Bomb Heads, D. E. Rosen, MRL Report 
201, May 1, 1945. 

11. Waterproofing of Spigot Gun Cartridges, R. S. Livingston, 
MRL Report 220, July 2, 1945. 

12. Delay Fuze for Spigot Gun, D. E. Rosen, MRL Report 
240, Aug. 28, 1945. 

13. Manufacturing specifications prepared by the Research 
and Development Branch of OSS will be found in the files 
of the Strategic Services Unit of the War Department. 


BIBLIOGRAPHY 


141 


Chapter 6 


1. Resume on Dust Explosions, C. S. Lu, Feb. 23, 1944. 

2. Memorandum, on Visit to Bruceton, C. S. Lu, Mar. 8, 1944. 

3. Memorandum on Some Preliminary Tests on Flour Ex- 
plosions, C. S. Lu, Mar. 20, 1944. 

4. Dust Explosions, a British appraisal, 1939. 

5. Use of Flour and Other Dust Explosions in Attacks on 
Confined Wooden Structures, C. S. Lu, MRL Report 92, 
June 6, 1944. 

6. Specification for Lulu Igniters, C. S. Lu, Sept. 6, 1944. 

7. Dust Explosion Tests in Wooden Houses Located at TV A 
Reservoir Area near Bryson City, N. C., C. S. Lu, MRL 
Report 152, Oct. 9, 1944. 

8. Memorandum on Latest Dust and Liquid Explosion Tests 
at Factory Mutual Test Station, C. S. Lu, Oct. 9, 1944. 

9. Acceptance Tests and User Trials of Production Lulus, 
C. S. Lu, MRL Report 180, Jan. 20, 1945. 

10. Test of Modified M-69 Incendiary Bombs Filled with 
Sulfur and Aluminum Powder ( SAL-X ), B. C. Kriete, 
Chemical Warfare Service TDMR Control 5004-915, 
p. 15. 

11. Progress Report for October 15-November 15, 1944, on 
Special Explosives {Teak), S. E. Eaton, Arthur D. Little, 
Inc., Nov. 24, 1944. 

12. Development of Salex , N. Thompson, Factory Mutual Re- 
search Corporation, Nov. 10, 1944. 

13. Final Report on Measurement of Explosion Effects in 
Building , Factory Mutual Research Corporation, Dec. 
31, 1944. 


14. Studies on SBX, Part I: Comparison of Various Com- 
bustibles as SBX under Confined Conditions, W. E. Gordon, 
Div. 2, NDRC, Nov. 15, 1944. 

15. Studies on SBX, Part II: Comparison of Results Obtained 
in Part I with Jones’ Simplified Theoretical Calculations 
of SBX Pressure Time Characteristics, C. S. Lu, MRL 
Report 167, Jan. 9, 1945, Addenda to Report 167, Feb. 
9, 1945. 

16. Use of Dust and Liquid Slow Burning Explosives in At- 
tacks on Confined Structures, C. S. Lu, MRL Report 183, 
Feb. 28, 1945. 

17. Final Report on Contract OEMsr-1023, H. J. Billings and 
S. E. Eaton, Jr., Div. 19, Serial No. 22, Part IX, May 24, 
1945. 

18. The Ignition of Wooden Structures; Part III, Ignition of a 
Wooden Hut, October 1944. 

19. Testing of Magnesium Dust Incendiaries as Developed by 
Dr. C. H. Bamford, C. S. Lu, MRL Report 178, Jan. 31, 
1945. 

20. Memorandum on the British Coal Dust Bombs, C. S. Lu, 
Feb. 19, 1944. 

21. An Improved Indicator for Measuring Static and Dynamic 
Pressure, C. E. Grinstead, R. N. Fraley, F. W. Chapman, 
and H. F. Schultz, presented at the National War Meeting 
of the Society of Automotive Engineers, Detroit, Mich., 
June 1944. 


Chapter 7 


1. Development of a Model of Bushmaster, G. Hammar, MRL 
Report 46, Feb. 17, 1944; A Single Shot Model Bush- 
master, G. Hammar, MRL Report 66, Apr. 3, 1944. 

2. Bushmaster — Third Report, G. Hammar, MRL Report 
113, July 21, 1944. 

3. Acceptance Test of Simulator, Rifle Fire ( Single Shot Bush- 
master), H. S. Isbin, MRL Report 179, Feb. 6, 1945; 
Acceptance Tests of Firing Device, Automatic Weapons, 


Delay Type, H. S. Isbin, MRL Report 192, Apr. 9, 1945; 
Acceptance Tests of Firing Device, Automatic Weapons, 
Pull Type, H. S. Isbin, MRL Report 194, Apr. 11, 1945; 
Acceptance Trial of Simulator Rifle Fire, H. S. Isbin, MRL 
Report 197, Apr. 19, 1945. 

4. Special Remote-Firing Devices, Operations Division Infor- 
mational Bulletin, Vol. 4, No. 3, Mar. 17, 1945. 


PART II 
Chapter 8 


1. No. 67 Concussion Detonator, L. H. Chase, Final Report, 
OEMsr-927, Div. 19, Serial No. 23, Jan. 1, 1945. 

2. Detonator, Concussion Type T-l, Corps of Engineers, En- 
gineer Board Tentative Specification EBP 556A, Apr. 3, 
1944. 

3. Concussion Detonators, Project DM-460, Technical Staff, 
Engineer Board, Fort Belvoir, Va., Mar. 4, 1944. 

4. Pressure Due to Explosion of TNT Under Water, chart pre- 
pared by David Taylor Model Basin, Navy Department, 
May 6, 1942. 


5. Passage of Beach and Underwater Obstacles, Report 811, 
Project DM-460, Engineer Board, Fort Belvoir, Va., May 
1, 1944. 

6. Tests of the Sympathetic Fuze (Memorandum), John R. 
Collins, Oct. 24, 1944. 

7. Acceptance Trial of the Sympathetic Fuze, British Report 
SS 1656, May 15, 1945. 

8. Dash-Pot Delay Arming Device (Silicone), Hubert N. 
Alyea, MRL Report 218, June 28, 1945. 

9. A Sympathetic Fuze for Air Operation , Gustaf Hammar, 
MRL Report 231, July 27, 1945. 


142 


BIBLIOGRAPHY 


10. Reducing the Effect of Turbulence on the Arming Time of 
Marine Type Sympathetic Fuzes , Reuben E. Wood, MRL 
Report 235, Aug. 10, 1945. 

11. Description of an Experimental BTL Model , G. B. Engle- 
hardt, May 7, 1943. 

12. Sympathetic Detonators XV, work report for July and 
August, G. B. Englehardt, Aug. 24, 1943. 

13. Preliminary Report on Depth Pressure Compensation , G. B. 
Englehardt, Sept. 14, 1943. 

14. Sympathetic Detonator, HEP-4, letter from C. D. Hocker 
to W. C. Lothrop, Sept. 16, 1943. 

15. Sympathetic Detonators XVII, report on work of Septem- 
ber-October, G. B. Englehardt, Nov. 2, 1943. 

16. Sympathetic Detonators XVIII, G. B. Englehardt, Nov. 
19, 1943. 


17. Sympathetic Detonator, Description of HEP Model No. 3, 
L. H. Chase, June 9, 1943. 

18. Sympathetic Detonators, L. H. Chase, Aug. 27, 1943. 

19. Behavior of Sympathetic Fuzes Under Water, II, C. S. Lu, 
MRL Report 110, July 19, 1944. 

20. Data on Salt Blocks for No. 67 Concussion Detonator, L. H. 
Chase, January 1945. 

21. Acceptance Test of Production Salt Plugs, H. S. Isbin, 
MRL Report 189, Mar. 27, 1945. 

22. Electrolytic Arming Cells , L. H. Chase, Aug. 15, 1944. 

23. Letter, R. L. Taylor to R. D. Torbert, Aug. 17, 1945. 

24. Concussion Detonator, L. H. Chase, Dec. 10, 1943. 

25. Manufacturing specifications prepared by the Research 
and Development Branch of OSS will be found in the 
files of the Strategic Services Unit of the War Department. 


Chapter 9 


1. Final Report on OEMsr-545, C. G. Fink and H. B. Lin- 
ford, Div. 19, Serial No. 24, Dec. 22, 1944. 

2. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 6, Feb. 15, 1943. 

3. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 7, May 3, 1943. 

4. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 8, June 1, 1943. 

5. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 9, June 2, 1943. 

6. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 10, June 21, 1943. 

7. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 11, Aug. 24, 1943. 

8. Studies on Reaction Rates of Solutions on Iron and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 12, Aug. 24, 1943. 

9. Studies an Reaction Rates of Solutions on Iran and Alloy 
Wire, C. G. Fink and H. B. Linford, Columbia University 
Report 13, Sept. 13, 1943. 

10. Analysis of Glycerol by Specific Gravity Methods for White 
and Blue Solutions, C. G. Fink and H. B. Linford, 
Columbia University Report 14, Dec. 4, 1943. 

11. Yellow Solution Studies, C. G. Fink and H. B. Linford, 
Columbia University Report 15, Dec. 16, 1943. 

12. Wicking Effects, C. G. Fink and H. B. Linford, Columbia 
University Report 16, Dec. 7, 1943. 

13. Analysis of Glycerol by Specific Gravity Methods for Green 
and Yellow Solutions, C. G. Fink and H. B. Linford, 
Columbia University Report 17, Dec. 16, 1943. 

14. Micro-Structure of SRA Wire, C. G. Fink and H. B. Lin- 
ford, Columbia University Report 18, July 18, 1944. 

15. Effect of Washing Copper Tubes in Sodium Hydroxide on 
Pencil Timings, C. G. Fink and H. B. Linford, Columbia 
University Report 19, December 1943. 


16. Analysis of Ampoules of Red Solution, C. G. Fink and 
H. B. Linford, Columbia Universitv Report 20, Dec. 7, 

1943. 

17. Relationship between Time and Specific Gravity at Constant 
Copper Chloride Content for SRA’s, C. G. Fink and 
H. B. Linford, Columbia University Report 21, Mar. 13, 

1944. 

18. Effect of Method of Spring Setting on Timing of SRA’s, 
C. G. Fink and H. B. Linford, Columbia University Re- 
port 22, Mar. 14, 1944. 

19. Specific Gravity of the Glycerol Copper Chloride Ampoule 
Solutions, C. G. Fink and H. B. Linford, Columbia Uni- 
versity Report 23, Mar. 23, 1944. 

20. The Effect of Solution Composition on Timing of SRA’s, 
C. G. Fink and H. B. Linford, Columbia University 
Report 24, June 1, 1944. 

21. Optimum Solutions for Green, Yellow, and Blue SRA’s, 
C. G. Fink and H. B. Linford, Columbia University Re- 
port 25, June 15, 1944. 

22. The Effect of pYL on Timings of SRA’s, C. G. Fink and 
H. B. Linford, Columbia University Report 26, Aug 11 
1944. 

23. Variations in Timings of SRA’s Observed Along a Typical 
Coil of Wire, C. G. Fink and H. B. Linford, Columbia 
University Report 27, Oct. 9, 1944. 

24. The Effect of Various Surface Treatments of the Wire on the 
Timings of SRA’s, C. G. Fink and H. B. Linford, Columbia 
University Report 28, Oct. 9, 1944. 

25. Further Studies on Optimum Solutions, C. G. Fink and 
H. B. Linford, Columbia University Report 29, Oct. 11, 
1944. 

26. The Effect of Plate Thickness for Electro-Galvanized Wires 
on Timings of SRA’s, C. G. Fink and H. B. Linford, 
Columbia University Report 30, Oct. 11, 1944. 

27. Tests on 3%-Day Delay SRA’s, C. G. Fink and H. B. 
Linford, Columbia University Report 31, Oct. 16, 
1944. 

28. Fatigue of SRA Springs, C. G. Fink and H. B. Linford, 
Columbia University Report 32, Oct. 17, 1944. 

29. Electro-Galvanizing of Music Wire, C. G. Fink and H. B. 
Linford, Columbia University Report 33, Dec. 28, 1944. 


BIBLIOGRAPHY 


143 


30. A Partial Statistical Analysis of the Results of Certain 
Tests of the Timing of Pencils SRA-2 , R. S. Livingston, 
MRL Report 24, Nov. 26, 1943. 

31. Chemical Research on Time Pencils , Interim Report on 
Extramural Work at Oxford , British Report, Oct. 29, 1943. 

32. Specification No. A1 for Switch No. 10, E.P.S. 6 (WD 
War Office, Whitehall), British Report, Dec. 1, 1943. 

33. Analysis of Glycerin Copper Chloride Mixtures, British 
Report DX. 14/HCL/4488, Dec. 9, 1943. 

34. Analysis of Dark Ampoule Solutions and Comparative Tim- 
ing Tests on Red Pencils Containing Dark and Light 
Solutions, R. S. Livingston, MRL Report 31, Jan. 6, 1944. 

35. Analysis of Glycerol Solutions by Means of the Abbe Re- 
fractometer, R. S. Livingston, MRL Report 39, Jan. 31, 
1944. 

36. Acceptance Tests for Cotton and Plasticine Submitted by 
Electrolux Corporation, H. S. Isbin, MRL Report 49, 
Feb. 17, 1944. 

37. Test of Linford's Modified Oxidimetric Method of Glycerol 
Analysis, R. S. Livingston, MRL Report 55, Feb. 23, 
1944. Correction to Report 55, Mar. 15, 1944. 

38. Special Acceptance Tests of Primers for SRA’s, R. S. 
Livingston and G. A. Noddin, MRL Report 57, Mar. 4, 
1944. 

39. Report on Timing of British SR’s Assembled in the A. C. 
Gilbert Plant, J. R. Collins, Mar. 30, 1944. 

40. Report on the Use of Preformed Cotton-Wool Plugs in Pro- 
duction, J. R. Collins, Apr. 21, 1944. 

41 . Effect of Orientation and Method of Crushing on the T imings 
of Red SRA-S’s, R. S. Livingston, MRL Report 75, Apr. 
26, 1944. 

42. Analysis of Functional Test Results, J. R. Collins, May 19, 
1944. 

43. Analysis of Glycerol Containing SR A Ampoule Solutions 
with the Aid of the Abbe Refractometer, R. S. Livingston, 
MRL Report 89, May 26, 1944. 


44. Test of Pencil Primer Sensitivity for Central and Eccentric 
Initiation, D. E. Severson, MRL Report 76, May 2, 1944. 

45. Report on Plungers, J. R. Collins, May 5, 1944. 

46. Corps of Engineers Field Manual FM 5-31, U. S. Army; 
Mines, Minefields, and Booby Traps, Royal Engineers, 
October 1943. 

47. Quality Control of Pencil Timed Fuzes, W. M. Fox, May 
26, 1944. 

48. Timings of SRA-S’s of all Colors at Temperatures between 0° 
and 150° F., R. S. Livingston, MRL Report 96, June 23, 

1944. 

49. Acceptance Tests of Polyvinyl Chloride Tubes for Use in 
SRA-3 Packaging, R. S. Livingston, MRL Report 117, 
Aug. 3, 1944. 

50. Effect of Orientation and Method of Crushing on the Timings 
of Glycerol Containing SRA-3’ s, R. S. Livingston, MRL 
Report 120, Aug. 12, 1944. 

51. A Chart of Operational Timings for SRA-S’s, R. S. Living- 
ston, Aug. 12, 1944. 

52. Corps of Engineers Tentative Specification No. T -1696 A, 
Firing Device Delay Type, M-l, Mar. 2, 1944. 

53. Switch No. 10, Conductometric Method for the Testing of 
Ampoule Solutions and the Determination of Glycerol, 
British Ministry of Supply, Chemical Inspection Depart- 
ment, Sept. 26, 1944. 

54. Prolonged Tropical Storage of Unpackaged and PVC 
Packaged Pencils, H. S. Isbin, MRL Report 172, Jan. 18, 

1945. 

55. Studies of Variations of the Time Pencil SR A, H. S. Isbin, 
MRL Report 228, July 16, 1945. 

56. A Report on American Pencil Production from December 
19^3 to August 1944, J. R. Collins. 

57. Minutes of a Conference on Pencil Research, R. S. Living- 
ston, Nov. 29, 1943; Meeting of a Subcommittee on Pencil 
Research, R. S. Livingston, Dec. 2, 1943. 


Chapter 10 


1. Test of 100 L&N G-3 Times, G. A. Perley, June 23, 1944. 

2. Time Delay Electrolytic Cell Mark II, G. A. Perley, July 
22, 1944. 

3. Progress Report of Work on Mark II, G. A. Perley, Aug. 21, 
1944. 

4. Progress Report on Work of Mark II, G. A. Perley, Sept. 
15, 1944; Mark II Pencil (Notes), W. M. Fox, Sept. 25, 
1944. 

5. Simulated Functional Test of the Springs for Perley’ s Pencil, 
D. E. Severson, MRL Report 142, Sept. 22, 1944. 

6. Progress Report on Work of Mark II Pencil , G. A. Perley, 
Nov. 1, 1944. 


7. Summary of Data on Mark II Pencils, G. A. Perley, May 
1, 1945. 

8. User Trial of the Electrolytic Time Pencil, R. S. Livingston, 
MRL Report 203, May 4, 1945. 

9. Mark II Time Pencil, J. A. Hamilton, CE SPENF EB 
400. 1 (DM 565), May 12, 1945. 

10. Final Report on Time Delay Controls, J. C. Peters, Final 
Report, OEMsr-876, Div. 19, Serial No. 31; Sec. 5, The 
Mark II Pencil, G. A. Perley, E. L. Eckfeldt, and R. D. 
Eanes, July 15, 1945. 


Chapter 11 


1. Report on Magnesium Igniter; Design, Production 
and Results of Test, Aaron Fischer, Final Report on 
Contract OEMsr-1119, Div. 19, Serial No. 28, Mar. 
18, 1945. 


2. Acceptance Tests of Magnesium-Headed SRI’s, R. S. 
Livingston, MRL Report 98, June 27, 1944; Confirmatory 
Acceptance Trial of SRI-Mg , R. S. Livingston, MRL Re- 
port 157, Nov. 3, 1944. 


^RESTRICTED \ 


144 


BIBLIOGRAPHY 


3. 

4. 

5. 


1 . 

2 . 

3. 

4. 

5. 

6 . 


1 . 


2 . 


3. 


4. 


1 . 


2 . 

3. 

4. 

5. 

6 . 


Static Initiation of AN-M50A2 and AN-M69 Incendiary 6. 
Bombs, D. E. Rosen, MRL Report 190, Mar. 3, 1945. 
Comparison of the Resistance to Weathering of Magnesium 7, 
and Pyroxoloid Headed Incendiary Pencils, R. S. Living- 
ston, MRL Report 43, Feb. 5, 1944. 8. 

The Magnesium-Headed Incendiary Pencil as a Separate 
Incendiary Igniter, R. S. Livingston, MRL Report 184, 

Feb. 19, 1945. 

Chapter 

Final Report on Time Delay Controls, J. C. Peters, Div. 

19, Serial No. 31; Part II, Mechanical Type Time Delay 
Mechanisms, B. J. Wilson, July 15, 1945. 

Progress Report on Mechanical Type Time Delay Mecha- 
nism, B. J. Wilson, Jan. 20, 1944. 

Specification for Clockwork Fuzes, British Report SS-323, 

Aug. 25, 1943. 

National Bureau of Standards Report on Synthetic Lubri- 
cant, L. J. Briggs, IDS:SBB VI-3/6307-209, Apr. 9, 1941. 
Functional and User Trial of Clock Fuze, Short Time, 

Mark I ( Eureka Clock), British Report, Jan. 5, 1944. 
Specifications for the Manufacture and Inspection of 


Silent Time Delayed Initiation of Safety Fuze (Memo- 
randum), R. S. Livingston, Apr. 25, 1945. 

Acceptance Trial of the Magnesium Matchhead, British 
Report, Reference Ln. 2868, May 31, 1945. 

Vest-Pocket Time Delay Incendiary, L. F. Fieser, Progress 
Report, Contract 11-186, OEMsr-179, Div. 11, OSRD 
Serial No. 1211, Harvard University, Feb. 19, 1943. 

12 

Demolition Firing Device Mark 3 ( Time Delay), Bureau of 
Ordnance, Navy Department, OS. 1528, March 1944. 

7. Summary of Reports of Tests on Recent Production , V. J. 
Porter, May 16, 1944. 

8. Special User Trial of Firing Device Clockwork (24 Hours), 
H. S. Isbin, MRL Report 193, Apr. 9, 1945; Acceptance 
Tests of Firing Device, Clockwork (24 Hours), H. S. Isbin, 
MRL Report 211, May 30, 1945. 

9. Acceptance Test of Modified Production Clockwork Fuzes, 
R. S. Livingston, MRL Report 80 A, July 10, 1944; 
Packaging Acceptance of Clockwork (12 Hours), H. S. 
Isbin, MRL Report 198, Apr. 25, 1945. 


Chapter 13 


Consolidated User Trial Report on AC Delay Mk II, 
British Report, Feb. 29, 1944. 

Attempted Development of a Short Time Mk I AC Delay by 
the Use of Certain Solvents, R. S. Livingston, MRL Report 
104, July 6, 1944; Adaptation of the Mk I AC Delay for 
Short Timings, R. S. Livingston, MRL Report 186, Mar. 
19, 1945; The Preparation of Short Time AC Delays for 
Training Purposes, R. S. Livingston, MRL Report 205, 
May 11, 1945. 

Attempt to Discover a Substitute Superior to Celluloid for 
Use as AC Delay Disc, R. S. Livingston, MRL Report 
109, July 20, 1944; Acceptance Trials of American Made 
AC Delay Celluloid Discs, R. S. Livingston, MRL Report 
122, Aug. 17, 1944. 

Development of Long Time Delays by the Use of Special 
Ampoules in Mk I AC Delays, R. S. Livingston, MRL 
Report 123, Aug. 18, 1944 ’, Acceptance Tests on Ampoules, 
AC Delay, Long Time, H. S. Isbin, MRL Report 207, 
May 16, 1945. 


5. Effect of Positioning on AC Delay Timings, MRL Memo- 
randum, R. S. Livingston, Dec. 15, 1944. 

6. Test of the Resistance of AC Delays to Temporary Deep 
Immersion, H. S. Isbin, MRL Report 212, June 1, 1945. 

7a. Synthetic Fibers for Special War Uses, J. C. Richards, 
R. A. Scheiderbauer, and W. W. Watkins, Final Report, 
OEMsr-1325, Div. 19, Serial No. 19, Dec. 4, 1944. 

7b. Ibid., Appendix A. 

8. Synthetic Fibers for Special War Uses, R. A. Scheider- 
bauer and J. C. Richards, Rayon Department, Technical 
Division, E. I. duPont de Nemours & Co., Feb. 2, 1944. 

9. Final Report on Time Delay Controls, J. C. Peters, Final 
Report on OEMsr-876, Div. 19, Serial No. 31, July 15, 
1945; Part 3, Magnesium Alloy Time Delays, G. A. Perley 
and R. D. Eanes; Part 4, The X-Ray Time Delay, G. A. 
Perley and R. D. Eanes. 

10. Porous Disc and Capillary Leak Fuses, Report 1, Oxford, 
Eng., June 7, 1944; Disc Time Delay, Report 2, Oct. 14, 1944. 

11. Functional Tests of U. S. Mark I AC Delays, R. S. Living- 
ston, MRL Report 108, July 13, 1944. 


Chapter 14 


SE Unit, D. Mitchell, Galvin Manufacturing Co., Dec. 
12, 1942. 

Report on Electrical Switch, D. Mitchell, Galvin Manu- 
facturing Co., June 5, 1943. 

Electrical Switch Report, D. Mitchell, Galvin Manu- 
facturing Co., July 22, 1943. 

Final Report on Radio Switch R-37( )/CR, R. S. Yoder, 
Final Report on OEMsr-378, May 15, 1944. 
Radio-Controlled Electric Switch — Improved Circuit Em- 
ploying Two Vacuum Tubes, R. W. Grigg, Western 
Electric Co., Inc., Apr. 26, 1944. 

Radio-Controlled Electric Switch — Modulating Unit, 
R. W. Grigg, Western Electric Co., Inc., June 15, 1944. 


7. A Radio-Controlled Switch for the 3-8 Megacycle Range, 
R. W. Grigg, Western Electric Co., Inc., Aug. 11, 1944; 
Appendix 1, Aug. 21, 1944. 

8. Radio-Controlled Electric Switch — Effect of Temperature 
on Battery Life , R. W. Grigg, Western Electric Co., Inc., 
Aug. 21, 1944. 

9. Radio-Controlled Electric Switch, Final Report on OEMsr- 
1158, R. W. Grigg, Western Electric Co., Inc., May 15, 
1945. 

10. Report on Radio-Controlled Delay, Radiation Laboratory 
Report, 61-PRB-022243, Feb. 22, 1943. 

11. The Willard Electrolytic Cell, E. M. Sutherland, Final 
Report on OEMsr-824, Div. 19, Serial No. 1, July 13, 1943. 


ESTR 


BIBLIOGRAPHY 


145 


PART III 

Chapter 15 


1. A Short-Range Induction Field Communicating System , 
Final Report, OEMsr-922, Div. 19, Serial No. 12, Part II, 
University of Pennsylvania, Moore School of Electrical 
Engineering, June 1945. 

la. Ibid., p. 18. 

2. Instruction Manual for Model B12 IFT, issued with each 
Model B12 IFT and included in reference 1 as Appendix 2. 

3. Instruction Manual for Model B8 IFL, issued with each 
Model B8 IFL, and inserted as Appendix 1 of reference 1. 

4. Memorandum for: Officer in Charge of Radio Section, De- 
partment Signal Office, APO 834, R. W. Martin, C.W.O., 
A.U.S. Report of Test of Induction Field Transceivers in a 


Panama Jungle, William J. Bartik, Moore School of 
Electrical Engineering, University of Pennsylvania, Aug. 
24, 1944. 

5. Test Reports of Marine Corps Equipment Board; Project 
No. 246; Marine Barracks, Quantico, Virginia, July 
1944. 

6. Memorandum for File , Project 43 ISC, Fred P. Morf and 
Robert Zeckiel, Camp Coles Signal Laboratory, Fort 
Monmouth, N. J., Mar. 24, 1945. 

7. Interoffice Memoranda, Field Demonstrations of IFT and 
IFL, Numbers 1, 2, 3, 4; References WA-4120, 6, 7, 8, 9, 
from Charles E. Waring to H. M. Chadwell. 


Chapter 16 


1. A System of Short-Range Communication by Passing 
Audio-Frequency Electric Currents Through Water, Final 
Report, OEMsr-922, Div. 19, Serial No. 12, Part IV, 
University of Pennsylvania, Moore School of Engineering, 
June 1945. 


2. Tests of Underwater Transmission Electric Current Re- 
ception, Robert Hills, Jr., and Carl W. Nelson, Jr., to Lt. 
Col. Shore, Communications Branch, OSS, Jan. 29, 1945. 

3. Reference 1 of Chapter 15, Appendix 8, T. H. Bonn, Uni- 
versity of Pennsylvania, May 16, 1945. 


Chapter 17 


1. A Microwave Transmitter-Receiver or Relay Station for 
Radiotelephone and Radiotelegraph Use , Final Report, 
OEMsr-922, Div. 19, Serial No. 12, Part V, University 
of Pennsylvania, Moore School of Engineering, June 1945. 


2. A Microwave Transmitter-Receiver or Relay Station for 
Radiotelephone and Radiotelegraph Use, Final Report, 
OEMsr-922, Div. 19, Serial No. 12, Part III, University 
of Pennsylvania, Moore School of Engineering, June 1945. 


PART IV 

Chapter 18 


1. An Audible Device for Locating Canisters Dropped from 
Planes, C. C. Chambers, R. M. Showers, and S. R. 
Warren, Jr., Final Report, OEMsr-922, Div. 19, Serial 
No. 12, Part I, June 12, 1944. 

2. Dropping Trial of Containers and Packages, Henlow, 
British Report DX14/ITCL/5041, Aug. 31, 1943. 

3. Report on Trial of Devices for Locating Containers in the 
Dark, British Report 576, trial held on Oct. 22, 1943. 

4. Test of Signaling Device, Project No. 136, J. Blades, Head- 


quarters Airborne Command, Camp McKall, N. C., 
Dec. 28, 1943. 

5. Report of User Trial Test of Locator, Parachute, Bell-Light 
Type, R. H. Forbes, May 28, 1945; Parachute Locator, 
Bell and Light Type, A. W. Martin, MRL Report 214, 
June 5, 1945. 

6. Functional and Acceptance Testing of Lost Chord, D. E. 
Severson, MRL Report 169, Jan. 9, 1945. 

7. Memorandum on the Mine Safety Appliance Company 
Locating Device, R. M. Showers, Feb. 4, 1944. 


Chapter 19 


1. Adhesives for Special Army and Navy Uses, Final Report, 
OEMsr-850, Div. 19, Serial No. 20, Researchand Develop- 
ment Department, Bakelite Corporation, Dec. 6, 1944. 

2. User Trial of Adhesive at Fort Belvoir, Virginia, W. C. 
Lothrop, Jan. 1, 1944; Functional Trial of the Adhesive at 
Fort Belvoir, Virginia, May 23, 1944 (Memorandum), 
W. C. Lothrop, June 2, 1944. 

3. Adhesives for Demolition Charges, Report 832, Technical 
Staff, Engineer Board, Fort Belvoir, Va., June 19, 1944. 


4. Acceptance Trial Tests of Adhesive RD-44-4U H. S. Isbin, 
MRL Report 130, Sept. 2, 1944. 

5. Report of the Functional Trial of Adhesives for Demolition 
Charges, British Report H1964, June 8, 1944; Report of the 
Functional Trial of the Bakelite Adhesive Preparation 
RD- 44 - 41 , British Report Reference 2347, Sept. 28, 
1944. 

6. Military Adhesives, Report 1674, Infantry Board, Fort 
Benning, Georgia, July 1944. 



146 


BIBLIOGRAPHY 


Chapter 20 


1. Balsam, H. J. Billings, Final Report, OEMsr-1023, Div. 
19, Serial No. 22, Part III, Arthur D. Little, Inc., Dec. 27, 
1944. 

2. User Trial of Balsam, H. S. Isbin, MRL Report 128, 
Aug. 29, 1944; Acceptance Test of Paper , Soluble, H. S. 
Isbin, MRL Report 200, May 1, 1945. 

3. Pyrofilm and Its Applications, E. B. Hershberg, Final 
Report, OEMsr-1214, Div. 19, Serial No. 30, Part III, 
Harvard University, May 28, 1945. 

4. Incendiary Document Cases, British Report, Oct. 12, 1944. 

5. Messenger Pouch Destroyer, E5 , L. W. Whitaker, C.W.S. 


TDMR 949, Jan. 6, 1945; Messenger Pouch Destroyer, 
L. F. Fieser and E. B. Hershberg, Final Report, OEMsr- 
1214, Div. 19, Serial No. 30, Part II, May 28, 1945. 

6. Container, Self -Destroying, Medium Size, Incendiary 
Pocket Notebook Type, H. S. Isbin, MRL Report 188, 
Mar. 27, 1945; Appendix, June 8, 1945. 

7. Moth, Explosive Brief Case Destroyer, D. E. Rosen, MRL 
Report 173, Jan. 22, 1945. 

8. Moth, Explosive Message Carrying Containers Small and 
Intermediate Size, D. E. Rosen, MRL Report 202, May 4 
1945. 


Chapter 21 


1. Dog Drag, H. J. Billings and E. C. Crocker, Final Report, 
OEMsr-1023, Div. 19, Serial No. 22, Part VII, Arthur D. 
Little, Inc., Apr. 30, 1945. 

2. Instructions for the Use of the Drag, British Report SS600, 
Jan. 5, 1943; Dog Drag, British Memorandum, Reference 
2097, Oct. 13, 1944. 

3. Report of Field Trial of Dog Drag at Quartermaster Re- 


mount Depot, Front Royal, Virginia, W. I. MacDonald, 
Aug. 3, 1944; Dog Drag User Trial Tests at Front Royal , 
Va., W. I. MacDonald, Aug. 29, 1944. 

4. Dog Drag Trials at Front Royal, Va., W. R. Clark, 
Oct. 15, 1944. 

5. Dog Drag, British Report 2249, Nov. 24, 1944. 


Chapter 22 


1. Comparison of Chlorine and Ozone as Viruscidal Agents 
of Poliomyelitis Virus, J. F. Kessel, D. K. Allison, F. J. 
Moore, M. Kaime, Proceedings of the Society for Ex- 
perimental Biology and Medicine, Vol. 53, May 1943, 
pp. 71-73. 

2. Report of Visits to Various Installations Interested in 
Water Purification by Portable Units, D. B. Summers, 
Aug. 21, 1944. 


3. Work on Aqua Vita Project, N. P. Nies, Maryland Re- 
search Laboratories, Feb. 1, 1945. 

4. Bags, Water Filter ( Millbank Type), British Provincial 
Specification E/1501, issued Jan. 29, 1945. 

5. A Small Filter-Type Water Purifier, R. E. Wood and 
L. B. Thomas, MRL Report 219, Aug. 13, 1945. 

6. A Study of Chemical Methods of Producing Small Quantities 
of Ozone, H. N. Alyea, MRL Report 232, Aug. 15, 1945. 


Chapter 23 


1. The Quieting of Outboard Motors, H. L. Ericson, OSRD 
Report 6188, Harvard University, Oct. 27, 1945. 

2. The Reduction of ftoise from Outboard Motors, L. D. 
Watkins; and Sound Level Reduction in Johnson Sea 
Horse Outboard Motors Models KSL-16 and POLR-5, 
W. C. Conover, Final Report, OEMsr-1427, Div. 19, 
Serial No. 37, Outboard, Marine & Manufacturing Com- 
pany, July 31, 1945. 

3. Report on the Functional Trial of the Silenced 22 HP 
Johnson Outboard Motor, British Report DBT/DAC/956, 
Aug. 13, 1944. 

J 4. Silencing Outboard Motors, L. L. Ryder, Consultant to 
OSRD Engineering and Transition Office, Mar. 17, 1945. 


5. Easy Starting of Outboard Motors, Outboard, Marine & 
Manufacturing Company, Apr. 23, 1945; Quick Starting 
of Outboard Motors, W. J. Matteson, Engineer Board 
Work Order DBR 3573, Apr. 9, 1945. 

1 6. Tentative Program for Silencing Johnson POLR Outboard 
Motor, L. L. Ryder, Apr. 23, 1945. 
j 7. 50 HP Evinrude Motor and Boat Silencing, L. L. Ryder, 
May 26, 1945; Noise Reduction of Chemold 32' Surf 
Boats Equipped with Evinrude 50 HP Motor, D. P. 
Loye, Engineering and Transition Office Contract 
OEMsr-1375, University of California at Los Angeles, 
Aug. 30, 1945. 


OSRD APPOINTEES 


DIVISION 19 

Chief 

Harris M. Chad well 


Technical Aide 

Warren C. Lothrop 


Members 


J. C. Boyce 
L. H. Farinholt 
T. R. Hogness 


F. L. Hovde 
R. W. King 

G. B. Kistiakowsky 

P. E. Klopsteg 


SECTION 19.1 

Chief 

George A. Richter 

Technical Aide 

Warren C. Lothrop 

Members 

Harris M. Cha dwell Arthur B. Lamb 

Warren C. Lothrop 


CONTRACT NUMBERS, CONTRACTORS, AND SUBJECT OF CONTRACTS 


Contract Number 

Name and Address of Contractor 

\ OEMsr-1023 

Arthur D. Little, Inc., 

Cambridge, Massachusetts 

OEMsr-850 

Bakelite Corporation, 

Bloomfield, New Jersey 

OEMsr-1254 

Eastman Kodak Company, 

Rochester, New York 

OEMsr-1325 

E. I. duPont de Nemours & Company, 
Wilmington, Delaware 

OEMsr-955 

Ford, Bacon & Davis, Inc., 

New York, New York 

OEMsr-927 

Holmes Electric Protective Company, 

New York, New York 

^ OEMsr-876 

Leeds and Northrup Company, 

Philadelphia, Pennsylvania 

OEMsr-1279 

Merz Engineering Company, 

Indianapolis, Indiana 

OEMsr-1427 

Outboard, Marine & Manufacturing Company, 
Waukegan and Evanston, Illinois 

OEMsr-1119 

Universal Match Corporation, 

St. Louis, Missouri 

OEMsr-739 

Galvin Manufacturing Company, 

Chicago, Illinois 

OEMsr-1158 

Western Electric Company, Inc., 

(with Division 13, NDRC) 

New York, New York 

OEMsr-824 

Willard Storage Battery Company, 

Cleveland, Ohio 

OEMsr-545 

Columbia University, 

New York, New York 

OEMsr-572 

Harvard University, 

Cambridge, Massachusetts 

OEMsr-1214 

Harvard University, 

Cambridge, Massachusetts 

OEMsr-602 

University of Chicago, 

Chicago, Illinois 

OEMsr-922 

University of Pennsylvania, 

Philadelphia, Pennsylvania 


Subject 


Development and testing of psychological 
weapons 

Development and testing of adhesives, in- 
cluding underwater adhesives 
Development of a hand grenade — Beano 

Studies and investigations in connection with 
delayed-action detonators 
Establishment, equipment, staffing, and man- 
agement of a central laboratory for testing 
and proving purposes in connection with 
the work of Division 19 
Development of various types of sympathetic 
and vibration fuzes, including relays 
Studies and investigations in connection with 
controlled delays 

Production design of Spigot Mortar 

Studies on silencing of marine engines 

Development of a special matchhead for use 
in delayed-action pocket incendiaries 
Studies and experimental investigations in 
connection with the construction of ampli- 
fiers and their associated mechanisms 
Studies and experimental investigations in 
connection with the construction of a radio- 
controlled switch 

Studies and experimental investigations in 
connection with the development and im- 
provement of an electrolytic cell 
Studies of the rates of reaction of iron with 
copper solution at different temperatures 
and of related problems in connection with 
controlled action 

Development of protective coating for water 
soluble wire 

Development of specially operated incendiary 
and pyrotechnic devices. 

Development of devices for the destruction of 
materials and the development of other 
offensive weapons 

Investigation of secret signaling and com- 
munication devices 


SERVICE PROJECT NUMBERS 


The projects listed below were transmitted to the Executive 
Secretary, NDRC, from the War or Navy Department 
through either the War Department Liaison Officer for 
NDRC or the Office of Research and Inventions (formerly 
the Coordinator of Research and Development), Navy 
Department. 


Service 

Project 

Number 


Subject 


White Phosphorus Grenade 

Bushmaster 

Oil Slick Igniters 


OD-176 

NR-109 

NO-234 


Other projects, forming the major portion of Division 19’s 
program, were received directly from the Office of Strategic 
Services. 



149 



INDEX 


The subject indexes of all STR volumes are combined in a master index printed in a separate volume. For access to 
the index volume consult the Army or Navy agency listed on the reverse of the half-title page. 


Abbe refractometer, 58 
Acetone celluloid delay fuze (AC De- 
lay), 80 

Adhesives, military; see Military ad- 
hesives 

Aluminum, use of; in grenade cases, 16 
in T-5 fuze, 18 
in WP Beano case, 23, 24 
Ammonium chloride solutions for Mark 
II pencils, 68 

Army rescue boat (ARB), 104 
Asbestos for military adhesives, 120 
Audio frequency generators, 109 

Baby Lulu (disperser-igniter), 36 
Bakelite, use in T-5 fuze, 17 
Bakelite cell for Mark II pencils, 68 
Barneys (outboard motor housings), 
135 

Barrier disc type magnesium alloy 
delay, 84 

Base for military adhesives, 120 
Battery exhaustion as basis for time 
delay fuze, 86 

Bazooka Rocket Launcher, 3 
Beano T-13, 15-22 
case, 16 

comparison with Mark II grenade, 19 
modifications, 22 
performance, 19, 20 
production, 20 
recommendations, 22 
requirements, 15 
T-5 fuze, 17, 20-21 
Beano, WP; see WP Beano 
Bentonite for military adhesives, 121 
Bickford fuze, 39 
Bowser piston pump, 129 
British; AC delay fuze, 80 
clockwork time delay, 74-79 
Cough Mixture (KOFQR) oil slick 
igniter, 8 

document destruction, 122 
dog deception, 127-128 
grenade No. 69, 17 
grenade No. 77, 27 
impact fuze, 17 
Mark I pencil, 54 
oil slick igniter, 8 
Sleeping Beauty, 100 
Spigot Mortar, 28-32 
sympathetic fuze, 45-53 
Bursoline, 129 

Bushmaster (remote firing device), 40 
Butacite for Mark I AC delay fuze, 81 
Butterfly cap for T-5 fuze, 17 

Calcium chloride solutions for Mark II 
pencils, 68 

Calcium phosphide for igniting oil 
slicks, 8 


Carbon black for military adhesives, 
120 

C-DC tablets, 129 

Celluloid for Mark I AC delay fuze, 81 
Celluloid matchhead for incendiary 
pencil, 71 

Ceramic plugs for water filters, 129 
Chloramine-T tablets, 129 
Chlor-dechlor tablets, 129 
City Slicker (oil slick igniter), 8 
Clockwork time delay, 74-79 
choice of clocks, 77 
multi-day model, 76-77 
performance, 77 
production, 78 
requirements, 74 
12-hour model, 74 
24-hour delay model, 76-79 
use by British, 74 
use by Germans, 74-79 
Coatings for pencil wire, 56 
Cold flow of metals, 86 
Collodion solution for Mark I pencil 
sealing, 61 

Communication systems, short range 
induction field (IFT-IFL), 95-99 
Communication with electric currents 
in water, 100-106 
Concussion Beano, 22 
Concussion detonator; see Sympathetic 
fuze 

Condenser microphone for ultrasonic 
measurements, 109 

Conductometric analysis of Mark I 
pencil ampoules, 58 
Cordura delay fuze, 82 
Corrosion as a timing mechanism in 
fuzes, 49 

“Cough Mixture” (KOFQR) oil slick 
igniter, 8 

CSR (Rectangular City Slicker), 8 
CST (Triangular City Slicker), 8, 12, 14 
Cyclotol for document container de- 
struction, 126 

Darex Thermoplastic Coating BM16, 
12 

Dash-pot delay fuze, 51 
Delay fuzes; see Time delay fuzes 
Demolition firing device Mark III, 
74-79 

Dental pellets; use in Mark I pencil, 61 
use in Mark II pencils, 68 
Disperser-igniter (Lulu), 34 
Diurnal temperature change, use in 
time delay fuze, 86 

Document destruction; edible paper, 
122 

explosive document containers, 125 
messenger pouch destroyer, 123 
pyrofilm, 122 
Dog deception, 127-128 


Dog drag, 128 
Dog trail, 128 

Edible paper, 122 

Electrogalvanized zinc coated wire for 
pencil (SRA-3), 56 

Electrolysis for ozone production, 132 
Electrolysis in time delay fuze, 85 
Electrolytic Arming Disc for fuzes, 49 
End plug for Mark II pencils, 68 
Ester gum for military adhesives, 120 
Ethylcellulose, use in WP Beano case, 
23, 24 

Eureka clock (clockwork time delay), 74 
Evinrude Lightfour outboard motor, 
133, 134 

Exhaust noise in outboard motors, 133 
Explosive document containers, 125 

Factory Mutual Research Corporation, 
37 

False trails for dog deception, 127 
Fast burning incendiary (FBI), 39 
Federal laboratories of Pittsburgh, 30 
Fiber G delay fuze, 83 
Filler for military adhesives, 120 
Filters, water, 129-136 
ceramic, 129 
filter pads, 130 
mechanical, 130 
metal, 130 
requirements, 129 
Firing devices; see also Fuzes 
delay type, M-l, 54 
special remote, 40 

Flash powder loading of Beano T-13, 22 
Fragmentation of Beano T-13, 19 
Free field room for acoustic measure- 
ments, 109 
Fuzes; Bickford, 39 
clockwork time delay, 74-79 
impact fuzes, 17, 19-22 
incendiary pencil (SRI), 71 
magnesium alloy delays, 83 
Mark I AC delay, 80 
Mark I pencil (SRA-3), 54-65 
Mark II pencil, 66-70 
organic fiber delays, 81 
radio-controlled switch, 87-91 
Spigot Mortar, 31 
sympathetic, 45-53 
T-5, 17 
T-21, 25 

Galton type ultrasonic whistle, 109 
Gas blown whistle for parachute loca- 
tion, 116 

Gas diffusion, use in time delay fuze, 86 
Gas supply of whistles for parachute 
location, 116 

Gauges for measuring SBX pressure, 
37, 38 

151 


152 


INDEX 


Geiger-Muller counter used for X-ray 
signaling, 108 
General Motors Corp., 37 
Glass diaphragm for sympathetic fuze, 
45 

Glycerol for time delay pencils, 57 
“Goop” for incendiary bombs, 8 
Grenade; see Hand grenades 

Halazone tablets, 129 
Hand grenades, 15-27 
cases, 16 

concussion Beano, 22 
Mark II, 15, 19 
T-13 Beano, 15-22 
T-13E1, 21 

Time Delay Beano, 22 
WP Beano, 23-27 
Handy-talky (SCR-536), 91 
Hercules blasting caps 100-24B, 84 
High frequency acoustic measurement, 
109 

Holmes Electric Protective Company, 
49 

Hooter (underwater sound source), 109 

IFL (Induction Field Locator), 95-99 
IFT (Induction Field Transceiver), 95- 
99 

Impact fuze; T5E1 fuze, 20 
T5E2 fuze, 20, 21 
T5E3 fuze, 22 
T-21 fuze, 25 
T-5 fuze, 17 
work of the British, 17 
Impact hand grenade; see Hand grenade 
Incendiary briefcase, 123 
Incendiary notebooks, 123 
Incendiary pencil (SRI), 71-73 
Induction field communication systems, 
short range, 95-99 

Induction Field Locator (IFL), 95-99 
Induction Field Transceiver (IFT), 95- 
99 

Intake noise in outboard motors, 134 
Intelligence aids, 122-126 
Intercommunication between ship and 
shore, 100 

Johnson K outboard motor, 133 
Johnson POLR outboard motor, 133 

Keikhaefer mercury rocket, 133 
Kidde whistle for parachute location, 
116-118 
Klystron, 107 


M-2 fuze lighter, 125 
Machine gun, remote firing device for, 
41 

Magnavox magneto, Navy Mark 22, 3 
Magnesium, use in FBI, 39 
Magnesium alloy delays, 83 
Magnesium matchhead for incendiary 
pencil, 71 

Magnetic protection for clockwork de- 
lays, 77 

Magneto, Navy Mark 22 Magnavox, 3 
Magnets, use in Bazooka firing, 3 
Mark I AC delay, 80 
Mark I pencil, 54-65 
ampoule solution, 57-60 
components, 55-62 
description and operation, 54 
history of development, 54 
performance, 65 
tension wire, 55 
testing, 62 
work of British, 54 
Mark II grenade, 19 
Mark II pencil, 66-70 
comparison with Mark I, 66 
components, 66 
description and operation, 66 
performance, 69 

Mark 15 standard WP smoke grenade, 
27 

Maryland Research Laboratories, 49 
Mechanical noise in outboard motors, 
135 

Mercury outboard motor, 134 
Messenger pouch destroyer, 123 
Metal diaphragms for sympathetic 
fuzes, 47 

Metal plugs for water filters, 130 
Methyl formate for AC delay ampoules, 
81 

Microfilter, Quinn, 129 
Microwave system for ^-mile com- 
munication, 107-111 
Military adhesives, 119-121 
manufacture, 121 
performance trials, 121 
plasticizer, 120 
RD-43-141, 120 
RD-44-41, 121 
requirements, 119 
theory, 119 

Millbank bag pre-filter for water puri- 
fication, 129 

Mine Safety Appliance Whistle, 117 
Mufflers for outboard motors, 134 
Multiple-shot Bushmaster (remote fir- 
ing device), 40 

Music wire for Mark I pencil, 55 


Landing craft, silencing of motors, 133- 
136 

Lethality of Beano T-13, 19 
“Lily cup” test for oil slick igniter 
No. 234, 12 

Liquid (viscous^flqfrv, use in time delay 
fuze, 83 

Lucite for ^rasaj|iirf#fRsHes, 109 
ITJLU^^i^W^r-igniter, 34 



Navy Mark 22 Magnavox magneto, 3 
Nitrated paper, 122 
Nitrocellulose, use in spigot mortar 
cartridge, 30 

Nitrocellulose plastic for pyrofilm, 123 
Noise reduction of outboard motors, 
133-136 

Nylon delay fuze, 82 


REGRADED UNCLAS5SE1ED 
ORDER SEC ARMY BY TAG PER jf 2 0 43 


Oil slick igniter No. 234, 8-14 
fuel charge, 8 
ignition system, 8 
“Lily cup” test, 12 
packaging, 12 
Paul Revere (PR), 8-9 
Rectangular City Slicker (CSR), 8-9 
steps in manufacture, 9 
tactical uses, 8, 14 
Triangular City Slicker (CST), 8 
Organic fiber delay fuze, 81 
Outboard motor, sound curtailment, 
133-136 

Ozone for water purification, genera- 
tion methods, 131 

Paper, edible, 122 

Parachute locating devices, 115-118 
Paul Revere (PR) oil slick igniter; 
construction, 9 
ignition, 8 
packaging, 12 
tests, 12 

Pencil (SRA-3); see Mark I pencil 
Pencil wire, 56, 66 

Pencils, incendiary; see Mark I pencil, 
Mark II pencil 

Pentolite; use in document container 
destroyers, 125 
use in rocket launchers, 6 
Permanente Mix (ignition fuze), 8 
Persulfate tablets for ozone production, 
132 

Phosphor bronze discs for fuze dia- 
phragms, 47 

Phosphorous oxidation for ozone pro- 
duction, 131 

Piston pump, Bowser, 129 
Plastic explosive, use in rocket launch- 
ers, 6 

Plasticizer for military adhesives, 120 
Polyvinyl butvrol (butacite) for Mark I 
delay, 81 

Polyvinyl chloride (PVC) used for pen- 
cil packaging, 62 

PR oil igniter (Paul Revere), 9-12 
Presstite fuel tank sealer SS-50, 9 
Propagation of electric currents in 
water, 100 
Pyrofilm, 122 

Pyrotechnic for messenger pouch de- 
struction, 125 

Quality control of Mark I pencil, 64 
Quinn microfilter, 129 

Radio controlled switch, 87-92 
aircraft modulating unit, 90 
operated at 10 megacycles, 91 
operated at 100 kilocycles, 87 
production, 87 
requirements, 87 
single tube model, 89 
two-tube model, 89, 90 
Radio detecting of parachute drop- 
pings, 115 

Radioactivity for parachute locating 
devices, 115 


3 


INDEX 


153 


RD-43-141 (Military adhesive), 120 
RD-44-41 (Military adhesive), 121 
Recommendations for future research; 
fuzes, 85 

hand grenades, 22 
IFL and IFT charges, 99 
induction field short-range communi- 
cations, 99 
MWT, 108 
UWT, 106 

Rectangular City Slicker (CSR) oil 
slick igniter, 8 
Refractometer, Abbe, 58 
Refractometric analysis of ampoule 
solutions, 58 

Release for Sympathetic Fuze, 45 
Remote-firing devices, 40-41 
Rocket, Keikhaefer mercury, 133 
Rocket launchers, 3-7 
Bazooka rockets, 3, 6 
spin stabilized rocket, 4 
Rosin for military adhesives, 120 
Rubber swelling, 86 

Salex, 34 

Salt blocks for fuzes, 46, 48, 49 
SBX; see Slow burning explosives 
“Scarlet Moo” (organic dye), 60 
Scatter bombs, 8 
SCR-536 handy-talky, 91 
Seitz K5 filter pad, i30 
Short distance signaling with X-rays 
and gamma rays, 108 
Short range communications with 
electric currents in w r ater, 100- 
106 

Short range induction field communica- 
ting system (IFT-IFL), 95-99 
Short range secret signaling systems, 
95-99 

Short time Mark I AC delay, 81 
Sight for Bazooka, 3 
Signal relay American model 3 (SR A-3) ; 
see Mark I pencil 

Signaling with X and gamma rays, 108 
Silencers for outboard motors, 133-136 
Silicone arming device for fuzes, 51 
“Sleeping Beauty,” British underwater 
craft, 100 

“Sleeping Beauty,” UWT model C-500 
installation, 104 

Slow burning explosives (SBX), 33-39 
dispenser-igniter, 34 
field performance, 38 
gauges for measuring pressure, 37, 38 
history of development, 33 
instruments for evaluation, 37 
limitations, 34 
Lulu, 34 
materials, 33, 34 


reasons for low efficiency, 34 
venting, 36 

Smoke grenade, Mark 15 Standard 
WP, 27 

Sodium alginate, cast, 122 
Sodium nitrate for pyrofilm, 123 
Spigot mortar, 28-32 
Spin Stabilized Rocket (SSR), 4 
SR A-3; see Mark I pencil 
SRI incendiary pencil, 71-73 
Standard delay fuze, 80 
Steel, use in grenade cases, 16, 23 
Strike-any where match, 71 
Sympathetic fuze, 45-53 
arming, 49 
dash-pot delay, 51 
electrolytic arming disc, 49 
fuze nos. 66 and 67, 47 
glass diaphragm, 45 
metal diaphragm, 47, 52 
performance in air, 47, 52 
performance in water, 51 
preliminary work by British, 45 
production, 53 
reed type, 53 
salt blocks, 49 
silicone arming disc, 51 

T-5 fuze, 17, 20-21 
T5E1 fuze, 20 
T5E2 fuze, 20 
T5E3 fuze, 22 

T-13 hand grenade; see Beano T-13 
T-21 fuze, 25 

Tactics for dog deception, 127 
Temperature change, diurnal, use in 
time delay fuze, 86 

Temperature coefficient for Mark I and 
Mark II pencils, 70 

Temperature coefficient of nylon delay 
fuzes, 82 

Time delay Beano, 22 
Time delay fuzes; clockwork, 74-79 
incendiary pencil (SRI), 71-73 
magnesium alloy, 83-85 
Mark I AC, 80-81 
Mark I pencil, 54-65 
Mark II pencil, 66-70 
organic fiber, 81-83 
use in Bazooka firing, 4 
use in PR ignition, 9 
use in SSR firing, 5 
use with Bushmaster, 40 
use with spigot mortar, 31 
Timings for AC delays, recommended, 
80 

Tourmaline piezo-electric gauges, 37 
Triangular City Slicker (CST) oil slick 
igniter, 8, 12, 14 
Triglycine hydrotriiodide, 129 


Ultrasonic measurement device, 109 
Ultrasonic whistle, 109 
Underwater exhaust for outboard mo- 
tors, 133 

Underwater telegraph and telephone 
(UWT); effect of noise, 101 
experimental models, 101 
modifications, 105 
performance tests, 104 
“Sleeping Beauty” tests, 104 
theory, 100 

UWT model C-101, 101 
UWT model C-102, 101 
UWT model C-103, 101 
UWT model C-104, 101 
UWT model C-105, 102 
UWT model C-201, 101 
UWT model C-206, 101 
UWT model C-301, 101 
UWT model C-500, 102 

Venting for SBX, 36 

Vibration test on clockwork delays, 77 

Vinylite (VMCH resin), 9 

Wallace and Tiernan portable filtering 
device, 129 

Water purifiers, 129-136 
C-DC tablets, 129 
ceramic filters, 129 
filter pads, 130 
mechanical filter, 130 
metal filters, 130 
ozone, 131 
requirements, 129 

Whistle (parachute locating devices), 
115-118 

construction, 116 
frequency, 116 
gas supply, 116 
Kidde model, 116-118 
Mine Safety Appliance model, 117 
performance tests on Kidde model, 
117, 118 

sound emitted, 1 16 

White phosphorous loading of Beano 
T-13, 23 

Workability of an adhesive, 119 
WP Beano (OD-176), 23-27 
case T-28, 23 

characteristics of various cases, 23-25 

fillings, 26 

performance, 26 

specifications, 23 

T-21 fuze, 25 


Yield value of an adhesive, 119 
Yoshino paper, 122 










































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